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<?php |
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namespace Kodus\Cache; |
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use DateInterval; |
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use Psr\SimpleCache\CacheInterface; |
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use Traversable; |
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/** |
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* WARNING! Don't use in production, only use for automated testing! |
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* |
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* This is a mock PSR-16 simple cache implementation - it's internal state survives only for the |
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* lifetime of the object itself. |
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*/ |
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class MockCache implements CacheInterface |
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{ |
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/** |
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* @var int |
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*/ |
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const DEFAULT_TTL = 86400; |
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/** |
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* @var string control characters for keys, reserved by PSR-16 |
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*/ |
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const PSR16_RESERVED = '/\{|\}|\(|\)|\/|\\\\|\@|\:/u'; |
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/** |
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* @var array map where cache key => serialized value |
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*/ |
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protected $cache = []; |
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/** |
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* @var int[] map where cache key => expiration timestamp |
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*/ |
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protected $cache_expiration = []; |
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/** |
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* @var int current frozen timestamp |
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*/ |
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protected $time; |
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/** |
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* @var int |
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*/ |
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protected $default_ttl; |
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/** |
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* @param int $default_ttl default time-to-live (in seconds) |
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*/ |
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public function __construct($default_ttl = self::DEFAULT_TTL) |
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{ |
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$this->default_ttl = $default_ttl; |
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$this->time = 0; |
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} |
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/** |
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* @param int $seconds |
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*/ |
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public function skipTime($seconds) |
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{ |
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$this->time += $seconds; |
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} |
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public function get($key, $default = null) |
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{ |
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$this->validateKey($key); |
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return isset($this->cache_expiration[$key]) && ($this->time < $this->cache_expiration[$key]) |
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? unserialize($this->cache[$key]) |
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: $default; |
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} |
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public function set($key, $value, $ttl = null) |
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{ |
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$this->validateKey($key); |
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if (is_int($ttl)) { |
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$expires_at = $this->time + $ttl; |
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} elseif ($ttl instanceof DateInterval) { |
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$expires_at = date_create_from_format("U", $this->time)->add($ttl)->getTimestamp(); |
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} elseif ($ttl === null) { |
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$expires_at = $this->time + $this->default_ttl; |
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} else { |
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throw new InvalidArgumentException("invalid TTL: " . print_r($ttl, true)); |
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} |
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$this->cache[$key] = serialize($value); |
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$this->cache_expiration[$key] = $expires_at; |
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return true; |
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} |
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public function delete($key) |
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{ |
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$this->validateKey($key); |
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$success = true; |
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if (! isset($this->cache[$key]) || ! isset($this->cache_expiration[$key])) { |
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$success = false; |
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} |
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unset($this->cache[$key]); |
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unset($this->cache_expiration[$key]); |
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return $success; |
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} |
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public function clear() |
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{ |
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$this->cache = []; |
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$this->cache_expiration = []; |
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} |
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public function getMultiple($keys, $default = null) |
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{ |
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if (! is_array($keys) && ! $keys instanceof Traversable) { |
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throw new InvalidArgumentException("keys must be either of type array or Traversable"); |
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} |
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$values = []; |
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foreach ($keys as $key) { |
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$this->validateKey($key); |
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$values[$key] = $this->get($key) ?: $default; |
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} |
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return $values; |
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} |
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public function setMultiple($values, $ttl = null) |
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{ |
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if (! is_array($values) && ! $values instanceof Traversable) { |
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throw new InvalidArgumentException("keys must be either of type array or Traversable"); |
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} |
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foreach ($values as $key => $value) { |
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$this->validateKey($key); |
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$this->set($key, $value, $ttl); |
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} |
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return true; |
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} |
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public function deleteMultiple($keys) |
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{ |
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if (! is_array($keys) && ! $keys instanceof Traversable) { |
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throw new InvalidArgumentException("keys must be either of type array or Traversable"); |
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} |
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foreach ($keys as $key) { |
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$this->validateKey($key); |
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$this->delete($key); |
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} |
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} |
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public function has($key) |
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{ |
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return $this->get($key, $this) !== $this; |
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} |
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protected function validateKey($key) |
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{ |
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if (preg_match(self::PSR16_RESERVED, $key, $match) === 1) { |
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throw new InvalidArgumentException("invalid character in key: {$match[0]}"); |
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} |
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} |
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} |
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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_function
expects aPost
object, and outputs the author of the post. The base classPost
returns a simple string and outputting a simple string will work just fine. However, the child classBlogPost
which is a sub-type ofPost
instead decided to return anobject
, and is therefore violating the SOLID principles. If aBlogPost
were passed tomy_function
, PHP would not complain, but ultimately fail when executing thestrtoupper
call in its body.