| 1 |  |  | <?php | 
                            
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                | 2 |  |  | /* | 
            
                                                                                                            
                            
            
                                    
            
            
                | 3 |  |  |  * Copyright (c) 2012-2014 Janos Szurovecz | 
            
                                                                                                            
                            
            
                                    
            
            
                | 4 |  |  |  * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 5 |  |  |  * Permission is hereby granted, free of charge, to any person obtaining a copy of | 
            
                                                                                                            
                            
            
                                    
            
            
                | 6 |  |  |  * this software and associated documentation files (the "Software"), to deal in | 
            
                                                                                                            
                            
            
                                    
            
            
                | 7 |  |  |  * the Software without restriction, including without limitation the rights to | 
            
                                                                                                            
                            
            
                                    
            
            
                | 8 |  |  |  * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies | 
            
                                                                                                            
                            
            
                                    
            
            
                | 9 |  |  |  * of the Software, and to permit persons to whom the Software is furnished to do | 
            
                                                                                                            
                            
            
                                    
            
            
                | 10 |  |  |  * so, subject to the following conditions: | 
            
                                                                                                            
                            
            
                                    
            
            
                | 11 |  |  |  * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 12 |  |  |  * The above copyright notice and this permission notice shall be included in all | 
            
                                                                                                            
                            
            
                                    
            
            
                | 13 |  |  |  * copies or substantial portions of the Software. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 14 |  |  |  * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 15 |  |  |  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | 
            
                                                                                                            
                            
            
                                    
            
            
                | 16 |  |  |  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | 
            
                                                                                                            
                            
            
                                    
            
            
                | 17 |  |  |  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | 
            
                                                                                                            
                            
            
                                    
            
            
                | 18 |  |  |  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | 
            
                                                                                                            
                            
            
                                    
            
            
                | 19 |  |  |  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | 
            
                                                                                                            
                            
            
                                    
            
            
                | 20 |  |  |  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | 
            
                                                                                                            
                            
            
                                    
            
            
                | 21 |  |  |  * SOFTWARE. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 22 |  |  |  */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 23 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 24 |  |  | namespace predaddy\domain; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 25 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 26 |  |  | use precore\lang\Object; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 27 |  |  | use precore\util\Objects; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 28 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 29 |  |  | /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 30 |  |  |  * It probably does not need to be used in application level. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 31 |  |  |  * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 32 |  |  |  * @see predaddy\domain\AbstractDomainEvent | 
            
                                                                                                            
                            
            
                                    
            
            
                | 33 |  |  |  * @author Janos Szurovecz <[email protected]> | 
            
                                                                                                            
                            
            
                                    
            
            
                | 34 |  |  |  */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 35 |  |  | final class NullAggregateId extends Object implements AggregateId | 
            
                                                                                                            
                            
            
                                    
            
            
                | 36 |  |  | { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 37 |  |  |     private static $instance; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 38 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 39 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 40 |  |  |      * @return NullAggregateId | 
            
                                                                                                            
                            
            
                                    
            
            
                | 41 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 42 |  |  |     public static function instance() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 43 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 44 |  |  |         return self::$instance; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 45 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 46 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 47 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 48 |  |  |      * Should not be called! | 
            
                                                                                                            
                            
            
                                    
            
            
                | 49 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 50 |  |  |     public static function init() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 51 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 52 |  |  |         self::$instance = new NullAggregateId(); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 53 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 54 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 55 |  |  |     private function __construct() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 56 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 57 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 58 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 59 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 60 |  |  |      * @return string | 
            
                                                                                                            
                            
            
                                    
            
            
                | 61 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 62 |  |  |     public function value() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 63 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 64 |  |  |         return ''; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 65 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 66 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 67 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 68 |  |  |      * @return string | 
            
                                                                                                            
                            
            
                                    
            
            
                | 69 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 70 |  |  |     public function aggregateClass() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 71 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 72 |  |  |         return ''; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 73 |  |  |     } | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 74 |  |  |  | 
            
                                                                        
                            
            
                                    
            
            
                | 75 |  |  |     public function toString() | 
            
                                                                        
                            
            
                                    
            
            
                | 76 |  |  |     { | 
            
                                                                        
                            
            
                                    
            
            
                | 77 |  |  |         return Objects::toStringHelper(__CLASS__)->toString(); | 
            
                                                                        
                            
            
                                    
            
            
                | 78 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 79 |  |  | } | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 80 |  |  | NullAggregateId::init(); | 
            
                                                        
            
                                    
            
            
                | 81 |  |  |  | 
            
                        
The PSR-1: Basic Coding Standard recommends that a file should either introduce new symbols, that is classes, functions, constants or similar, or have side effects. Side effects are anything that executes logic, like for example printing output, changing ini settings or writing to a file.
The idea behind this recommendation is that merely auto-loading a class should not change the state of an application. It also promotes a cleaner style of programming and makes your code less prone to errors, because the logic is not spread out all over the place.
To learn more about the PSR-1, please see the PHP-FIG site on the PSR-1.