| 1 |  |  | <?php | 
            
                                                                                                            
                            
            
                                    
            
            
                | 2 |  |  | /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 3 |  |  |  * Src/Cache/Cache.php | 
            
                                                                                                            
                            
            
                                    
            
            
                | 4 |  |  |  * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 5 |  |  |  * @package     Ds\Cache | 
            
                                                                                                            
                            
            
                                    
            
            
                | 6 |  |  |  * @subpackage  Cache | 
            
                                                                                                            
                            
            
                                    
            
            
                | 7 |  |  |  * @author      Dan Smith <[email protected]> | 
            
                                                                                                            
                            
            
                                    
            
            
                | 8 |  |  |  * @version     v.1 (20/03/2017) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 9 |  |  |  * @copyright   Copyright (c) 2017, Dan Smith | 
            
                                                                                                            
                            
            
                                    
            
            
                | 10 |  |  |  */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 11 |  |  | namespace Ds\Cache; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 12 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 13 |  |  | use Psr\SimpleCache\CacheInterface as SimpleCache; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 14 |  |  | use Psr\SimpleCache\DateInterval; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 15 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 16 |  |  | /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 17 |  |  |  * PSR 16 Simple Cache Component | 
            
                                                                                                            
                            
            
                                    
            
            
                | 18 |  |  |  * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 19 |  |  |  * @package Ds\Cache | 
            
                                                                                                            
                            
            
                                    
            
            
                | 20 |  |  |  */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 21 |  |  | class Cache extends AbstractCache implements SimpleCache | 
            
                                                                                                            
                            
            
                                    
            
            
                | 22 |  |  | { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 23 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 24 |  |  |      * Persists data in the cache, uniquely referenced by a key with an optional expiration TTL time. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 25 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 26 |  |  |      * @param string                $key   The key of the item to store. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 27 |  |  |      * @param mixed                 $value The value of the item to store, must be serializable. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 28 |  |  |      * @param null|int|\DateInterval $ttl   Optional. The TTL value of this item. If no value is sent and | 
            
                                                                                                            
                            
            
                                    
            
            
                | 29 |  |  |      *                                     the driver supports TTL then the library may set a default value | 
            
                                                                                                            
                            
            
                                    
            
            
                | 30 |  |  |      *                                     for it or let the driver take care of that. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 31 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 32 |  |  |      * @return bool True on success and false on failure. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 33 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 34 |  |  |      * @throws \Psr\SimpleCache\InvalidArgumentException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 35 |  |  |      *   MUST be thrown if the $key string is not a legal value. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 36 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 37 | 3 |  |     public function set($key, $value, $ttl = null) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 38 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 39 |  |  |         //convert to timestamp from now. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 40 | 3 |  |         if ($ttl instanceof \DateInterval){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 41 | 1 |  |             $dateTime = new \DateTime(); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 42 | 1 |  |             $dateTime->add( $ttl ); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 43 | 1 |  |             $ttl = $dateTime->getTimestamp() - time(); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 44 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 45 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 46 | 3 |  |         if (!is_int($ttl) ||  $ttl === null){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 47 | 1 |  |             throw new InvalidArgumentException('$ttl can only be an instance of \DateInterval, int or null'); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 48 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 49 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 50 | 2 |  |         return $this->cache->set($key, $value, $ttl); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 51 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 52 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 53 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 54 |  |  |      * Determines whether an item is present in the cache. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 55 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 56 |  |  |      * NOTE: It is recommended that has() is only to be used for cache warming type purposes | 
            
                                                                                                            
                            
            
                                    
            
            
                | 57 |  |  |      * and not to be used within your live applications operations for get/set, as this method | 
            
                                                                                                            
                            
            
                                    
            
            
                | 58 |  |  |      * is subject to a race condition where your has() will return true and immediately after, | 
            
                                                                                                            
                            
            
                                    
            
            
                | 59 |  |  |      * another script can remove it making the state of your app out of date. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 60 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 61 |  |  |      * @param string $key The cache item key. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 62 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 63 |  |  |      * @return bool | 
            
                                                                                                            
                            
            
                                    
            
            
                | 64 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 65 |  |  |      * @throws \Psr\SimpleCache\InvalidArgumentException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 66 |  |  |      *   MUST be thrown if the $key string is not a legal value. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 67 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 68 | 3 |  |     public function has($key) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 69 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 70 | 3 |  |         $this->_isValidKey($key); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 71 | 2 |  |         return $this->cache->has($key); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 72 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 73 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 74 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 75 |  |  |      * Fetches a value from the cache. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 76 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 77 |  |  |      * @param string $key     The unique key of this item in the cache. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 78 |  |  |      * @param mixed  $default Default value to return if the key does not exist. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 79 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 80 |  |  |      * @return mixed The value of the item from the cache, or $default in case of cache miss. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 81 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 82 |  |  |      * @throws \Psr\SimpleCache\InvalidArgumentException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 83 |  |  |      *   MUST be thrown if the $key string is not a legal value. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 84 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 85 | 3 |  |     public function get($key, $default = null) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 86 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 87 | 3 |  |         $this->_isValidKey($key); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 88 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 89 | 2 |  |         if ($this->cache->has($key)){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 90 | 1 |  |             return $this->cache->get($key); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 91 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 92 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 93 | 1 |  |         return $default; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 94 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 95 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 96 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 97 |  |  |      * Delete an item from the cache by its unique key. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 98 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 99 |  |  |      * @param string $key The unique cache key of the item to delete. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 100 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 101 |  |  |      * @return bool True if the item was successfully removed. False if there was an error. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 102 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 103 |  |  |      * @throws \Psr\SimpleCache\InvalidArgumentException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 104 |  |  |      *   MUST be thrown if the $key string is not a legal value. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 105 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 106 | 1 |  |     public function delete($key) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 107 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 108 | 1 |  |         $this->_isValidKey($key); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 109 | 1 |  |         return $this->cache->delete($key); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 110 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 111 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 112 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 113 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 114 |  |  |      * Obtains multiple cache items by their unique keys. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 115 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 116 |  |  |      * @param \iterable $keys    A list of keys that can obtained in a single operation. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 117 |  |  |      * @param mixed    $default Default value to return for keys that do not exist. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 118 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 119 |  |  |      * @return \iterable A list of key => value pairs. Cache keys that do not exist or are stale will have $default as value. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 120 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 121 |  |  |      * @throws \Psr\SimpleCache\InvalidArgumentException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 122 |  |  |      *   MUST be thrown if $keys is neither an array nor a Traversable, | 
            
                                                                                                            
                            
            
                                    
            
            
                | 123 |  |  |      *   or if any of the $keys are not a legal value. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 124 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 125 | 1 |  |     public function getMultiple($keys, $default = null) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 126 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 127 | 1 |  |         $this->_isTraversable($keys); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 128 | 1 |  |         $result = []; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 129 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 130 | 1 |  |         foreach ((array)$keys as $key){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 131 | 1 |  |             $cachedItem = $this->cache->get($key); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 132 | 1 |  |             $result[$key] = (null !== $cachedItem) ? $cachedItem : $default; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 133 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 134 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 135 | 1 |  |         return (array)$result; | 
                            
                    |  |  |  | 
                                                                                        
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                | 136 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 137 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 138 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 139 |  |  |      * Persists a set of key => value pairs in the cache, with an optional TTL. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 140 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 141 |  |  |      * @param \iterable              $values A list of key => value pairs for a multiple-set operation. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 142 |  |  |      * @param null|int|DateInterval $ttl    Optional. The TTL value of this item. If no value is sent and | 
            
                                                                                                            
                            
            
                                    
            
            
                | 143 |  |  |      *                                      the driver supports TTL then the library may set a default value | 
            
                                                                                                            
                            
            
                                    
            
            
                | 144 |  |  |      *                                      for it or let the driver take care of that. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 145 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 146 |  |  |      * @return bool True on success and false on failure. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 147 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 148 |  |  |      * @throws \Psr\SimpleCache\InvalidArgumentException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 149 |  |  |      *   MUST be thrown if $values is neither an array nor a Traversable, | 
            
                                                                                                            
                            
            
                                    
            
            
                | 150 |  |  |      *   or if any of the $values are not a legal value. | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 151 |  |  |      */ | 
            
                                                                        
                            
            
                                    
            
            
                | 152 | 2 |  |     public function setMultiple($values, $ttl = null) | 
            
                                                                        
                            
            
                                    
            
            
                | 153 |  |  |     { | 
            
                                                                        
                            
            
                                    
            
            
                | 154 | 2 |  |         $this->_hasKeys($values); | 
            
                                                                        
                            
            
                                    
            
            
                | 155 | 2 |  |         $this->_isTraversable($values); | 
            
                                                                        
                            
            
                                    
            
            
                | 156 | 2 |  |         $results = []; | 
            
                                                                        
                            
            
                                    
            
            
                | 157 |  |  |  | 
            
                                                                        
                            
            
                                    
            
            
                | 158 | 2 |  |         foreach ((array)$values as $key => $value){ | 
            
                                                                        
                            
            
                                    
            
            
                | 159 | 2 |  |             $results[] = $this->cache->set($key, $value, $ttl); | 
            
                                                                        
                            
            
                                    
            
            
                | 160 |  |  |         } | 
            
                                                                        
                            
            
                                    
            
            
                | 161 |  |  |  | 
            
                                                                        
                            
            
                                    
            
            
                | 162 | 2 |  |         if ($this->_hasFailure($results)){ | 
            
                                                                        
                            
            
                                    
            
            
                | 163 | 1 |  |             return false; | 
            
                                                                        
                            
            
                                    
            
            
                | 164 |  |  |         } | 
            
                                                                        
                            
            
                                    
            
            
                | 165 |  |  |  | 
            
                                                                        
                            
            
                                    
            
            
                | 166 | 1 |  |         return true; | 
            
                                                                        
                            
            
                                    
            
            
                | 167 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 168 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 169 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 170 |  |  |      * Deletes multiple cache items in a single operation. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 171 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 172 |  |  |      * @param \iterable $keys A list of string-based keys to be deleted. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 173 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 174 |  |  |      * @return bool True if the items were successfully removed. False if there was an error. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 175 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 176 |  |  |      * @throws \Psr\SimpleCache\InvalidArgumentException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 177 |  |  |      *   MUST be thrown if $keys is neither an array nor a Traversable, | 
            
                                                                                                            
                            
            
                                    
            
            
                | 178 |  |  |      *   or if any of the $keys are not a legal value. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 179 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 180 | 2 |  |     public function deleteMultiple($keys) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 181 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 182 | 2 |  |         $this->_isTraversable($keys); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 183 | 2 |  |         $results = []; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 184 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 185 | 2 |  |         foreach ((array)$keys as $key){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 186 | 2 |  |             $results[] = $this->cache->delete($key); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 187 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 188 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 189 | 2 |  |         if ($this->_hasFailure($results)){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 190 | 1 |  |             return false; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 191 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 192 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 193 | 1 |  |         return true; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 194 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 195 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 196 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 197 |  |  |      * Wipes clean the entire cache's keys. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 198 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 199 |  |  |      * @return bool True on success and false on failure. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 200 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 201 | 1 |  |     public function clear() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 202 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 203 | 1 |  |         return $this->cache->clear(); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 204 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 205 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 206 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 207 |  |  |      * Check that provided key is valid. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 208 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 209 |  |  |      * @param $key | 
            
                                                                                                            
                            
            
                                    
            
            
                | 210 |  |  |      * @throws InvalidArgumentException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 211 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 212 | 7 |  |     private function _isValidKey($key){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 213 | 7 |  |         if (!is_string($key)){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 214 | 2 |  |             throw new InvalidArgumentException('provided key must be a valid string'); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 215 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 216 | 5 |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 217 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 218 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 219 |  |  |      * Check that $keys are traversable | 
            
                                                                                                            
                            
            
                                    
            
            
                | 220 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 221 |  |  |      * @param $data | 
            
                                                                                                            
                            
            
                                    
            
            
                | 222 |  |  |      * @throws InvalidArgumentException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 223 |  |  |      * @return bool | 
            
                                                                                                            
                            
            
                                    
            
            
                | 224 |  |  |      * @internal | 
            
                                                                                                            
                            
            
                                    
            
            
                | 225 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 226 | 8 |  |     private function _isTraversable($data){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 227 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 228 | 8 |  |         if (is_array($data) || $data instanceof \Traversable){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 229 | 7 |  |             return true; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 230 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 231 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 232 | 1 |  |         throw new InvalidArgumentException('Keys must be traversable'); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 233 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 234 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 235 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 236 |  |  |      * @param array $arr | 
            
                                                                                                            
                            
            
                                    
            
            
                | 237 |  |  |      * @return bool | 
            
                                                                                                            
                            
            
                                    
            
            
                | 238 |  |  |      * @throws InvalidArgumentException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 239 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 240 | 4 |  |     private function _hasKeys(array $arr) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 241 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 242 | 4 |  |         if (array() === $arr || array_keys($arr) === range(0, count($arr) - 1)){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 243 | 1 |  |             throw new InvalidArgumentException('Keys missing'); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 244 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 245 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 246 | 3 |  |         return true; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 247 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 248 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 249 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 250 |  |  |      * Check for failures when adding multiple entries. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 251 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 252 |  |  |      * @param array $results | 
            
                                                                                                            
                            
            
                                    
            
            
                | 253 |  |  |      * @return bool | 
            
                                                                                                            
                            
            
                                    
            
            
                | 254 |  |  |      * @internal | 
            
                                                                                                            
                            
            
                                    
            
            
                | 255 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 256 | 6 |  |     private function _hasFailure(array $results){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 257 | 6 |  |         if (in_array(false, $results)){ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 258 | 3 |  |             return true; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 259 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 260 | 3 |  |         return false; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 261 |  |  |     } | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 262 |  |  | } | 
            
                                                        
            
                                    
            
            
                | 263 |  |  |  | 
            
                        
If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_functionexpects aPostobject, and outputs the author of the post. The base classPostreturns a simple string and outputting a simple string will work just fine. However, the child classBlogPostwhich is a sub-type ofPostinstead decided to return anobject, and is therefore violating the SOLID principles. If aBlogPostwere passed tomy_function, PHP would not complain, but ultimately fail when executing thestrtouppercall in its body.