| 1 |  |  | <?php | 
            
                                                                                                            
                            
            
                                    
            
            
                | 2 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 3 |  |  | /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 4 |  |  |  * This file is part of the PHP Generics package. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 5 |  |  |  * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 6 |  |  |  * @package Generics | 
            
                                                                                                            
                            
            
                                    
            
            
                | 7 |  |  |  */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 8 |  |  | namespace Generics\Streams; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 9 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 10 |  |  | use Generics\FileExistsException; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 11 |  |  | use Generics\NoAccessException; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 12 |  |  | use Generics\LockException; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 13 |  |  | use Generics\Lockable; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 14 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 15 |  |  | /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 16 |  |  |  * This class provides a file output stream. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 17 |  |  |  * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 18 |  |  |  * @author Maik | 
            
                                                                                                            
                            
            
                                    
            
            
                | 19 |  |  |  */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 20 |  |  | class FileOutputStream implements OutputStream, Lockable | 
            
                                                                                                            
                            
            
                                    
            
            
                | 21 |  |  | { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 22 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 23 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 24 |  |  |      * The file handle | 
            
                                                                                                            
                            
            
                                    
            
            
                | 25 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 26 |  |  |      * @var resource | 
            
                                                                                                            
                            
            
                                    
            
            
                | 27 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 28 |  |  |     private $handle; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 29 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 30 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 31 |  |  |      * The absolute file path and name | 
            
                                                                                                            
                            
            
                                    
            
            
                | 32 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 33 |  |  |      * @var string | 
            
                                                                                                            
                            
            
                                    
            
            
                | 34 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 35 |  |  |     private $fileName; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 36 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 37 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 38 |  |  |      * Whether resource is locked | 
            
                                                                                                            
                            
            
                                    
            
            
                | 39 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 40 |  |  |      * @var boolean | 
            
                                                                                                            
                            
            
                                    
            
            
                | 41 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 42 |  |  |     private $locked; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 43 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 44 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 45 |  |  |      * Create a new FileOutputStream | 
            
                                                                                                            
                            
            
                                    
            
            
                | 46 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 47 |  |  |      * @param string $file | 
            
                                                                                                            
                            
            
                                    
            
            
                | 48 |  |  |      *            The absolute (or relative) path to file to write into. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 49 |  |  |      * @param boolean $append | 
            
                                                                                                            
                            
            
                                    
            
            
                | 50 |  |  |      *            Whether to append the data to an existing file. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 51 |  |  |      * @throws FileExistsException will be thrown in case of file exists and append is set to false. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 52 |  |  |      * @throws NoAccessException will be thrown in case of it is not possible to write to file. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 53 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 54 | 24 |  |     public function __construct($file, $append = false) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 55 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 56 | 24 |  |         $this->locked = false; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 57 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 58 | 24 |  |         $mode = "wb"; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 59 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 60 | 24 |  |         if (file_exists($file)) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 61 | 3 |  |             if (! $append) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 62 | 1 |  |                 throw new FileExistsException("File $file already exists!"); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 63 |  |  |             } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 64 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 65 | 2 |  |             if (! is_writable($file)) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 66 |  |  |                 throw new NoAccessException("Cannot write to file $file"); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 67 |  |  |             } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 68 | 2 |  |             $mode = "ab"; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 69 | 2 |  |         } else { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 70 | 22 |  |             if (! is_writable(dirname($file))) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 71 |  |  |                 throw new NoAccessException("Cannot write to file {file}", array( | 
            
                                                                                                            
                            
            
                                    
            
            
                | 72 |  |  |                     'file' => $file | 
            
                                                                                                            
                            
            
                                    
            
            
                | 73 |  |  |                 )); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 74 |  |  |             } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 75 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 76 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 77 | 23 |  |         $this->handle = fopen($file, $mode); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 78 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 79 | 23 |  |         if (! $this->ready()) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 80 |  |  |             throw new StreamException("Could not open {file} for writing", array( | 
            
                                                                                                            
                            
            
                                    
            
            
                | 81 |  |  |                 'file' => $file | 
            
                                                                                                            
                            
            
                                    
            
            
                | 82 |  |  |             )); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 83 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 84 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 85 | 23 |  |         $this->fileName = $file; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 86 | 23 |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 87 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 88 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 89 |  |  |      * Cleanup (e.g. release lock) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 90 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 91 | 23 |  |     public function __destruct() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 92 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 93 |  |  |         try { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 94 | 23 |  |             if ($this->locked) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 95 | 2 |  |                 $this->unlock(); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 96 | 2 |  |             } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 97 | 23 |  |         } catch (\Generics\GenericsException $ex) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 98 |  |  |             // Do nothing | 
            
                                                                                                            
                            
            
                                    
            
            
                | 99 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 100 | 23 |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 101 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 102 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 103 |  |  |      * {@inheritDoc} | 
            
                                                                                                            
                            
            
                                    
            
            
                | 104 |  |  |      * @see \Generics\Streams\Stream::ready() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 105 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 106 |  |  |     public function ready() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 107 | 23 |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 108 |  |  |         return is_resource($this->handle); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 109 | 23 |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 110 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 111 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 112 |  |  |      * {@inheritDoc} | 
            
                                                                                                            
                            
            
                                    
            
            
                | 113 |  |  |      * @see \Generics\Streams\OutputStream::write() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 114 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 115 |  |  |     public function write($buffer) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 116 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 117 | 18 |  |         if (! $this->ready()) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 118 |  |  |             throw new StreamException("Stream is not open!"); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 119 | 18 |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 120 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 121 |  |  |         if ($buffer instanceof InputStream) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 122 |  |  |             $in = clone $buffer; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 123 | 18 |  |             assert($in instanceof InputStream); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 124 | 14 |  |             while ($in->ready()) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 125 | 14 |  |                 $buf = $in->read(1024); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 126 | 14 |  |                 if (fwrite($this->handle, $buf) != strlen($buf)) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 127 | 14 |  |                     throw new StreamException("Could not write memory stream into file"); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 128 | 14 |  |                 } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 129 |  |  |             } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 130 |  |  |         } else { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 131 | 14 |  |             $buffer = strval($buffer); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 132 | 14 |  |             if (fwrite($this->handle, $buffer) != strlen($buffer)) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 133 | 4 |  |                 throw new StreamException("Could not write buffer into file"); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 134 | 4 |  |             } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 135 |  |  |             fflush($this->handle); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 136 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 137 | 4 |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 138 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 139 | 18 |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 140 |  |  |      * {@inheritDoc} | 
            
                                                                                                            
                            
            
                                    
            
            
                | 141 |  |  |      * @see \Generics\Streams\Stream::close() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 142 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 143 |  |  |     public function close() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 144 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 145 |  |  |         if (is_resource($this->handle)) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 146 | 20 |  |             fclose($this->handle); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 147 |  |  |             $this->handle = null; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 148 | 20 |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 149 | 20 |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 150 | 20 |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 151 | 20 |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 152 | 20 |  |      * {@inheritDoc} | 
            
                                                                                                            
                            
            
                                    
            
            
                | 153 |  |  |      * @see \Countable::count() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 154 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 155 |  |  |     public function count() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 156 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 157 |  |  |         if (! $this->ready()) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 158 |  |  |             throw new StreamException("Stream is not open!"); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 159 | 2 |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 160 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 161 | 2 |  |         return ftell($this->handle); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 162 | 1 |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 163 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 164 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 165 | 1 |  |      * Retrieve the file path and name | 
            
                                                                                                            
                            
            
                                    
            
            
                | 166 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 167 |  |  |      * @return string | 
            
                                                                                                            
                            
            
                                    
            
            
                | 168 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 169 |  |  |     public function __toString() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 170 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 171 |  |  |         return realpath($this->fileName); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 172 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 173 | 1 |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 174 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 175 | 1 |  |      * {@inheritDoc} | 
            
                                                                                                            
                            
            
                                    
            
            
                | 176 |  |  |      * @see \Generics\Streams\OutputStream::isWriteable() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 177 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 178 |  |  |     public function isWriteable() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 179 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 180 |  |  |         return $this->ready(); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 181 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 182 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 183 | 1 |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 184 |  |  |      * {@inheritDoc} | 
            
                                                                                                            
                            
            
                                    
            
            
                | 185 | 1 |  |      * @see \Generics\Streams\OutputStream::flush() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 186 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 187 |  |  |     public function flush() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 188 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 189 |  |  |         if (! $this->ready()) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 190 |  |  |             throw new StreamException("Stream is not open!"); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 191 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 192 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 193 | 15 |  |         fflush($this->handle); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 194 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 195 | 15 |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 196 | 1 |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 197 |  |  |      * {@inheritDoc} | 
            
                                                                                                            
                            
            
                                    
            
            
                | 198 |  |  |      * @see \Generics\Lockable::lock() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 199 | 14 |  |      */ | 
            
                                                                                                            
                            
            
                                                                    
                                                                                                        
            
            
                | 200 | 14 | View Code Duplication |     public function lock() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 201 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 202 |  |  |         if ($this->locked || flock($this->handle, LOCK_EX) === false) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 203 |  |  |             throw new LockException("Could not acquire lock"); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 204 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 205 |  |  |         $this->locked = true; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 206 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 207 | 3 |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 208 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 209 | 3 |  |      * {@inheritDoc} | 
            
                                                                                                            
                            
            
                                    
            
            
                | 210 | 1 |  |      * @see \Generics\Lockable::unlock() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 211 |  |  |      */ | 
            
                                                                                                            
                            
            
                                                                    
                                                                                                        
            
            
                | 212 | 3 | View Code Duplication |     public function unlock() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 213 | 3 |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 214 |  |  |         if (!$this->locked || flock($this->handle, LOCK_UN) === false) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 215 |  |  |             throw new LockException("Could not release lock"); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 216 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 217 |  |  |         $this->locked = false; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 218 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 219 |  |  |      | 
            
                                                                                                            
                            
            
                                    
            
            
                | 220 | 4 |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 221 |  |  |      * {@inheritDoc} | 
            
                                                                                                            
                            
            
                                    
            
            
                | 222 | 4 |  |      * @see \Generics\Lockable::isLocked() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 223 | 1 |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 224 |  |  |     public function isLocked() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 225 | 3 |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 226 | 3 |  |     	return $this->locked; | 
                            
                    |  |  |  | 
                                                                                        
                                                                                     | 
            
                                                                                                            
                            
            
                                    
            
            
                | 227 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 228 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 229 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 230 |  |  |      * {@inheritDoc} | 
            
                                                                                                            
                            
            
                                    
            
            
                | 231 |  |  |      * @see \Generics\Streams\Stream::isOpen() | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 232 |  |  |      */ | 
            
                                                        
            
                                    
            
            
                | 233 |  |  |     public function isOpen() | 
            
                                                        
            
                                    
            
            
                | 234 |  |  |     { | 
            
                                                        
            
                                    
            
            
                | 235 |  |  |     	return is_resource($this->handle); | 
            
                                                        
            
                                    
            
            
                | 236 |  |  |     } | 
            
                                                        
            
                                    
            
            
                | 237 |  |  | } | 
            
                                                        
            
                                    
            
            
                | 238 |  |  |  | 
            
                        
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.