| 1 |  |  | <?php | 
            
                                                                                                            
                            
            
                                    
            
            
                | 2 |  |  | /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 3 |  |  |  * Copyright (c) 2016-2016} Andreas Heigl<[email protected]> | 
            
                                                                                                            
                            
            
                                    
            
            
                | 4 |  |  |  * Permission is hereby granted, free of charge, to any person obtaining a copy | 
            
                                                                                                            
                            
            
                                    
            
            
                | 5 |  |  |  * of this software and associated documentation files (the "Software"), to deal | 
            
                                                                                                            
                            
            
                                    
            
            
                | 6 |  |  |  * in the Software without restriction, including without limitation the rights | 
            
                                                                                                            
                            
            
                                    
            
            
                | 7 |  |  |  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | 
            
                                                                                                            
                            
            
                                    
            
            
                | 8 |  |  |  * copies of the Software, and to permit persons to whom the Software is | 
            
                                                                                                            
                            
            
                                    
            
            
                | 9 |  |  |  * furnished to do so, subject to the following conditions: | 
            
                                                                                                            
                            
            
                                    
            
            
                | 10 |  |  |  * The above copyright notice and this permission notice shall be included in | 
            
                                                                                                            
                            
            
                                    
            
            
                | 11 |  |  |  * all copies or substantial portions of the Software. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 12 |  |  |  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | 
            
                                                                                                            
                            
            
                                    
            
            
                | 13 |  |  |  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | 
            
                                                                                                            
                            
            
                                    
            
            
                | 14 |  |  |  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | 
            
                                                                                                            
                            
            
                                    
            
            
                | 15 |  |  |  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | 
            
                                                                                                            
                            
            
                                    
            
            
                | 16 |  |  |  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | 
            
                                                                                                            
                            
            
                                    
            
            
                | 17 |  |  |  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | 
            
                                                                                                            
                            
            
                                    
            
            
                | 18 |  |  |  * THE SOFTWARE. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 19 |  |  |  * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 20 |  |  |  * @author    Andreas Heigl<[email protected]> | 
            
                                                                                                            
                            
            
                                    
            
            
                | 21 |  |  |  * @copyright 2016-2016 Andreas Heigl | 
            
                                                                                                            
                            
            
                                    
            
            
                | 22 |  |  |  * @license   http://www.opensource.org/licenses/mit-license.php MIT-License | 
            
                                                                                                            
                            
            
                                    
            
            
                | 23 |  |  |  * @version   0.0 | 
            
                                                                                                            
                            
            
                                    
            
            
                | 24 |  |  |  * @since     27.03.2016 | 
            
                                                                                                            
                            
            
                                    
            
            
                | 25 |  |  |  * @link      http://github.com/heiglandreas/callingallpapers | 
            
                                                                                                            
                            
            
                                    
            
            
                | 26 |  |  |  */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 27 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 28 |  |  | namespace Callingallpapers\Writer; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 29 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 30 |  |  | use Symfony\Component\Console\Formatter\OutputFormatterInterface; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 31 |  |  | use Symfony\Component\Console\Output\OutputInterface; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 32 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 33 |  |  | class NullOutput implements OutputInterface | 
            
                                                                                                            
                            
            
                                    
            
            
                | 34 |  |  | { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 35 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 36 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 37 |  |  |      * Returns whether verbosity is debug (-vvv). | 
            
                                                                                                            
                            
            
                                    
            
            
                | 38 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 39 |  |  |      * @return bool true if verbosity is set to VERBOSITY_DEBUG, false otherwise | 
            
                                                                                                            
                            
            
                                    
            
            
                | 40 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 41 |  |  |     public function isDebug() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 42 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 43 |  |  |         return false; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 44 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 45 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 46 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 47 |  |  |      * Sets output formatter. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 48 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 49 |  |  |      * @param OutputFormatterInterface $formatter | 
            
                                                                                                            
                            
            
                                    
            
            
                | 50 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 51 |  |  |      * @api | 
            
                                                                                                            
                            
            
                                    
            
            
                | 52 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 53 |  |  |     public function setFormatter(OutputFormatterInterface $formatter) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 54 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 55 |  |  |         // TODO: Implement setFormatter() method. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 56 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 57 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 58 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 59 |  |  |      * Returns whether verbosity is verbose (-v). | 
            
                                                                                                            
                            
            
                                    
            
            
                | 60 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 61 |  |  |      * @return bool true if verbosity is set to VERBOSITY_VERBOSE, false otherwise | 
            
                                                                                                            
                            
            
                                    
            
            
                | 62 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 63 |  |  |     public function isVerbose() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 64 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 65 |  |  |         return false; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 66 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 67 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 68 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 69 |  |  |      * Returns whether verbosity is very verbose (-vv). | 
            
                                                                                                            
                            
            
                                    
            
            
                | 70 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 71 |  |  |      * @return bool true if verbosity is set to VERBOSITY_VERY_VERBOSE, false otherwise | 
            
                                                                                                            
                            
            
                                    
            
            
                | 72 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 73 |  |  |     public function isVeryVerbose() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 74 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 75 |  |  |         return false; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 76 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 77 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 78 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 79 |  |  |      * Writes a message to the output. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 80 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 81 |  |  |      * @param string|array $messages The message as an array of lines or a single string | 
            
                                                                                                            
                            
            
                                    
            
            
                | 82 |  |  |      * @param bool         $newline  Whether to add a newline | 
            
                                                                                                            
                            
            
                                    
            
            
                | 83 |  |  |      * @param int          $type     The type of output (one of the OUTPUT constants) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 84 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 85 |  |  |      * @throws \InvalidArgumentException When unknown output type is given | 
            
                                                                                                            
                            
            
                                    
            
            
                | 86 |  |  |      * @api | 
            
                                                                                                            
                            
            
                                    
            
            
                | 87 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 88 |  |  |     public function write( | 
            
                                                                                                            
                            
            
                                    
            
            
                | 89 |  |  |         $messages, | 
            
                                                                                                            
                            
            
                                    
            
            
                | 90 |  |  |         $newline = false, | 
            
                                                                                                            
                            
            
                                    
            
            
                | 91 |  |  |         $type = self::OUTPUT_NORMAL | 
            
                                                                                                            
                            
            
                                    
            
            
                | 92 |  |  |     ) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 93 |  |  |         // TODO: Implement write() method. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 94 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 95 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 96 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 97 |  |  |      * Writes a message to the output and adds a newline at the end. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 98 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 99 |  |  |      * @param string|array $messages The message as an array of lines or a single string | 
            
                                                                                                            
                            
            
                                    
            
            
                | 100 |  |  |      * @param int          $type     The type of output (one of the OUTPUT constants) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 101 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 102 |  |  |      * @throws \InvalidArgumentException When unknown output type is given | 
            
                                                                                                            
                            
            
                                    
            
            
                | 103 |  |  |      * @api | 
            
                                                                                                            
                            
            
                                    
            
            
                | 104 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 105 |  |  |     public function writeln($messages, $type = self::OUTPUT_NORMAL) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 106 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 107 |  |  |         // TODO: Implement writeln() method. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 108 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 109 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 110 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 111 |  |  |      * Sets the verbosity of the output. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 112 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 113 |  |  |      * @param int $level The level of verbosity (one of the VERBOSITY constants) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 114 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 115 |  |  |      * @api | 
            
                                                                                                            
                            
            
                                    
            
            
                | 116 |  |  |      */public function setVerbosity($level) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 117 |  |  | { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 118 |  |  |     // TODO: Implement setVerbosity() method. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 119 |  |  | } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 120 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 121 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 122 |  |  |      * Gets the current verbosity of the output. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 123 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 124 |  |  |      * @return int The current level of verbosity (one of the VERBOSITY constants) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 125 |  |  |      * @api | 
            
                                                                                                            
                            
            
                                    
            
            
                | 126 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 127 |  |  |     public function getVerbosity() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 128 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 129 |  |  |         return 0; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 130 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 131 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 132 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 133 |  |  |      * Sets the decorated flag. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 134 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 135 |  |  |      * @param bool $decorated Whether to decorate the messages | 
            
                                                                                                            
                            
            
                                    
            
            
                | 136 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 137 |  |  |      * @api | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 138 |  |  |      */ | 
            
                                                                        
                            
            
                                    
            
            
                | 139 |  |  |     public function setDecorated($decorated) | 
            
                                                                        
                            
            
                                    
            
            
                | 140 |  |  |     { | 
            
                                                                        
                            
            
                                    
            
            
                | 141 |  |  |         // TODO: Implement setDecorated() method. | 
            
                                                                        
                            
            
                                    
            
            
                | 142 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 143 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 144 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 145 |  |  |      * Gets the decorated flag. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 146 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 147 |  |  |      * @return bool true if the output will decorate messages, false otherwise | 
            
                                                                                                            
                            
            
                                    
            
            
                | 148 |  |  |      * @api | 
            
                                                                                                            
                            
            
                                    
            
            
                | 149 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 150 |  |  |     public function isDecorated() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 151 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 152 |  |  |         return 0; | 
                            
                    |  |  |  | 
                                                                                        
                                                                                     | 
            
                                                                                                            
                            
            
                                    
            
            
                | 153 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 154 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 155 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 156 |  |  |      * Returns current output formatter instance. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 157 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 158 |  |  |      * @return OutputFormatterInterface | 
            
                                                                                                            
                            
            
                                    
            
            
                | 159 |  |  |      * @api | 
            
                                                                                                            
                            
            
                                    
            
            
                | 160 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 161 |  |  |     public function getFormatter() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 162 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 163 |  |  |         // TODO: Implement getFormatter() method. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 164 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 165 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 166 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 167 |  |  |      * Returns whether verbosity is quiet (-q). | 
            
                                                                                                            
                            
            
                                    
            
            
                | 168 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 169 |  |  |      * @return bool true if verbosity is set to VERBOSITY_QUIET, false otherwise | 
            
                                                                                                            
                            
            
                                    
            
            
                | 170 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 171 |  |  |     public function isQuiet() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 172 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 173 |  |  |         // TODO: Implement isQuiet() method. | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 174 |  |  |     } | 
            
                                                        
            
                                    
            
            
                | 175 |  |  | } | 
            
                        
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.