| 
                    1
                 | 
                                    
                                                     | 
                
                 | 
                <?php  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    2
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    3
                 | 
                                    
                                                     | 
                
                 | 
                namespace Scaffolder\Compilers\Core;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    4
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    5
                 | 
                                    
                                                     | 
                
                 | 
                use Carbon\Carbon;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    6
                 | 
                                    
                                                     | 
                
                 | 
                use Illuminate\Support\Facades\File;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    7
                 | 
                                    
                                                     | 
                
                 | 
                use Scaffolder\Compilers\AbstractCompiler;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    8
                 | 
                                    
                                                     | 
                
                 | 
                use Scaffolder\Compilers\Support\FileToCompile;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    9
                 | 
                                    
                                                     | 
                
                 | 
                use Scaffolder\Compilers\Support\PathParser;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    10
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    11
                 | 
                                    
                                                     | 
                
                 | 
                class MigrationCompiler extends AbstractCompiler  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    12
                 | 
                                    
                                                     | 
                
                 | 
                { | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    13
                 | 
                                    
                                                     | 
                
                 | 
                	private $date;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    14
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    15
                 | 
                                    
                                                     | 
                
                 | 
                	protected $cachePrefix 	= 'migration_';  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    16
                 | 
                                    
                                                     | 
                
                 | 
                	protected $stubFilename = 'Migration.php' ;  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
                | 
                    17
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                        
                            
            
                                    
            
            
                | 
                    18
                 | 
                                    
                                                     | 
                
                 | 
                	public function __construct($scaffolderConfig, $modelData = null)  | 
            
            
                                                                        
                            
            
                                    
            
            
                | 
                    19
                 | 
                                    
                                                     | 
                
                 | 
                	{ | 
            
            
                                                                        
                            
            
                                    
            
            
                | 
                    20
                 | 
                                    
                                                     | 
                
                 | 
                		$this->stubsDirectory = __DIR__ . '/../../../../stubs/Api/';  | 
            
            
                                                                        
                            
            
                                    
            
            
                | 
                    21
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                        
                            
            
                                    
            
            
                | 
                    22
                 | 
                                    
                                                     | 
                
                 | 
                		parent::__construct($scaffolderConfig, $modelData);  | 
            
            
                                                                        
                            
            
                                    
            
            
                | 
                    23
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                        
                            
            
                                    
            
            
                | 
                    24
                 | 
                                    
                                                     | 
                
                 | 
                		$this->date = Carbon::now();  | 
            
            
                                                                        
                            
            
                                    
            
            
                | 
                    25
                 | 
                                    
                                                     | 
                
                 | 
                	}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    26
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    27
                 | 
                                    
                                                     | 
                
                 | 
                	/**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    28
                 | 
                                    
                                                     | 
                
                 | 
                	 * Replace and store the Stub.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    29
                 | 
                                    
                                                     | 
                
                 | 
                	 *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    30
                 | 
                                    
                                                     | 
                
                 | 
                	 * @return string  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    31
                 | 
                                    
                                                     | 
                
                 | 
                	 */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    32
                 | 
                                    
                                                     | 
                
                 | 
                	public function replaceAndStore()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    33
                 | 
                                    
                                                     | 
                
                 | 
                	{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    34
                 | 
                                    
                                                     | 
                
                 | 
                		  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    35
                 | 
                                    
                                                     | 
                
                 | 
                		return $this->addFields()  | 
            
                            
                    | 
                        
                     | 
                     | 
                     | 
                    
                                                                                                    
                        
                         
                                                                                        
                                                                                     
                     | 
                
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    36
                 | 
                                    
                                                     | 
                
                 | 
                					->store(new FileToCompile(false, $this->modelData->modelHash));  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    37
                 | 
                                    
                                                     | 
                
                 | 
                		  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    38
                 | 
                                    
                                                     | 
                
                 | 
                	}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    39
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    40
                 | 
                                    
                                                     | 
                
                 | 
                	/**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    41
                 | 
                                    
                                                     | 
                
                 | 
                	 * Get output filename  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    42
                 | 
                                    
                                                     | 
                
                 | 
                	 *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    43
                 | 
                                    
                                                     | 
                
                 | 
                	 *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    44
                 | 
                                    
                                                     | 
                
                 | 
                	 * @return $this  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    45
                 | 
                                    
                                                     | 
                
                 | 
                	 */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    46
                 | 
                                    
                                                     | 
                
                 | 
                	protected function getOutputFilename()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    47
                 | 
                                    
                                                     | 
                
                 | 
                	{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    48
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    49
                 | 
                                    
                                                     | 
                
                 | 
                		return  PathParser::parse($this->scaffolderConfig->generator->paths->migrations) . $this->date->format('Y_m_d_') . str_pad($this->modelData->migrationOrder, 2, 0, STR_PAD_LEFT) . '_create_' . strtolower($this->modelName) . '_table.php'; | 
            
                            
                    | 
                        
                     | 
                     | 
                     | 
                    
                                                                                                    
                        
                         
                                                                                        
                                                                                     
                     | 
                
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    50
                 | 
                                    
                                                     | 
                
                 | 
                	}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    51
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    52
                 | 
                                    
                                                     | 
                
                 | 
                	/**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    53
                 | 
                                    
                                                     | 
                
                 | 
                	 * Add fields.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    54
                 | 
                                    
                                                     | 
                
                 | 
                	 *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    55
                 | 
                                    
                                                     | 
                
                 | 
                	 * @param $modelData  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    56
                 | 
                                    
                                                     | 
                
                 | 
                	 *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    57
                 | 
                                    
                                                     | 
                
                 | 
                	 * @return $this  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    58
                 | 
                                    
                                                     | 
                
                 | 
                	 */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    59
                 | 
                                    
                                                     | 
                
                 | 
                	private function addFields()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    60
                 | 
                                    
                                                     | 
                
                 | 
                	{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    61
                 | 
                                    
                                                     | 
                
                 | 
                		// Default primary key  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    62
                 | 
                                    
                                                     | 
                
                 | 
                		$fields = "\t\t\t\$table->increments('id');" . PHP_EOL . PHP_EOL; | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    63
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    64
                 | 
                                    
                                                     | 
                
                 | 
                		// Check primary key  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    65
                 | 
                                    
                                                     | 
                
                 | 
                		# TODO FIX, primary  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    66
                 | 
                                    
                                                     | 
                
                 | 
                		  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    67
                 | 
                                    
                                                     | 
                
                 | 
                		foreach ($this->modelData->fields as $field)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    68
                 | 
                                    
                                                     | 
                
                 | 
                		{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    69
                 | 
                                    
                                                     | 
                
                 | 
                			$parsedModifiers = '';  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    70
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    71
                 | 
                                    
                                                     | 
                
                 | 
                			if($field->index == "primary")  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    72
                 | 
                                    
                                                     | 
                
                 | 
                				continue ;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    73
                 | 
                                    
                                                     | 
                
                 | 
                			if($this->modelData->timeStamps && $field->name == "created_at")  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    74
                 | 
                                    
                                                     | 
                
                 | 
                				continue ;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    75
                 | 
                                    
                                                     | 
                
                 | 
                			if($this->modelData->timeStamps && $field->name == "updated_at")  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    76
                 | 
                                    
                                                     | 
                
                 | 
                				continue ;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    77
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    78
                 | 
                                    
                                                     | 
                
                 | 
                			// Check modifiers  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    79
                 | 
                                    
                                                     | 
                
                 | 
                			if (!empty($field->modifiers))  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    80
                 | 
                                    
                                                     | 
                
                 | 
                			{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    81
                 | 
                                    
                                                     | 
                
                 | 
                				$modifiersArray = explode(':', $field->modifiers); | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    82
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    83
                 | 
                                    
                                                     | 
                
                 | 
                				foreach ($modifiersArray as $modifier)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    84
                 | 
                                    
                                                     | 
                
                 | 
                				{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    85
                 | 
                                    
                                                     | 
                
                 | 
                					$modifierAndValue = explode(',', $modifier); | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    86
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    87
                 | 
                                    
                                                     | 
                
                 | 
                					if (count($modifierAndValue) == 2)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    88
                 | 
                                    
                                                     | 
                
                 | 
                					{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    89
                 | 
                                    
                                                     | 
                
                 | 
                						$parsedModifiers .= '->' . $modifierAndValue[0] . '(' . $modifierAndValue[1] . ')'; | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    90
                 | 
                                    
                                                     | 
                
                 | 
                					}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    91
                 | 
                                    
                                                     | 
                
                 | 
                					else  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    92
                 | 
                                    
                                                     | 
                
                 | 
                					{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    93
                 | 
                                    
                                                     | 
                
                 | 
                						$parsedModifiers .= '->' . $modifierAndValue[0] . '()';  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    94
                 | 
                                    
                                                     | 
                
                 | 
                					}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    95
                 | 
                                    
                                                     | 
                
                 | 
                				}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    96
                 | 
                                    
                                                     | 
                
                 | 
                			}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    97
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    98
                 | 
                                    
                                                     | 
                
                 | 
                			// Check foreign key for unsigned modifier  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    99
                 | 
                                    
                                                     | 
                
                 | 
                			if ($field->foreignKey)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    100
                 | 
                                    
                                                     | 
                
                 | 
                			{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    101
                 | 
                                    
                                                     | 
                
                 | 
                				$parsedModifiers .= '->unsigned()';  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    102
                 | 
                                    
                                                     | 
                
                 | 
                			}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    103
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    104
                 | 
                                    
                                                     | 
                
                 | 
                			// Check indexes  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    105
                 | 
                                    
                                                     | 
                
                 | 
                			if ($field->index != 'none')  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    106
                 | 
                                    
                                                     | 
                
                 | 
                			{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    107
                 | 
                                    
                                                     | 
                
                 | 
                				$fields .= sprintf("\t\t\t\$table->%s('%s')%s->%s();" . PHP_EOL, $field->type->db, $field->name, $parsedModifiers, $field->index); | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    108
                 | 
                                    
                                                     | 
                
                 | 
                			}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    109
                 | 
                                    
                                                     | 
                
                 | 
                			else  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    110
                 | 
                                    
                                                     | 
                
                 | 
                			{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    111
                 | 
                                    
                                                     | 
                
                 | 
                				if ($field->type->db == "enum") { | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    112
                 | 
                                    
                                                     | 
                
                 | 
                					$items = '';  | 
            
            
                                                                                                            
                            
            
                                                                    
                                                                                                        
            
            
                | 
                    113
                 | 
                                    
                                                     | 
                
                View Code Duplication | 
                					foreach ($field->options as $key => $option) { | 
            
                            
                    | 
                        
                     | 
                     | 
                     | 
                    
                                                                                                    
                        
                         
                                                                                        
                                                                                     
                     | 
                
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    114
                 | 
                                    
                                                     | 
                
                 | 
                						$items .= "'" . $option . "'";  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    115
                 | 
                                    
                                                     | 
                
                 | 
                						if ($key < (count($field->options) - 1))  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    116
                 | 
                                    
                                                     | 
                
                 | 
                							$items .= ", ";  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    117
                 | 
                                    
                                                     | 
                
                 | 
                					}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    118
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    119
                 | 
                                    
                                                     | 
                
                 | 
                					$fields .= sprintf("\t\t\t\$table->%s('%s', array(%s));" . PHP_EOL, $field->type->db, $field->name, $items); | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    120
                 | 
                                    
                                                     | 
                
                 | 
                				}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    121
                 | 
                                    
                                                     | 
                
                 | 
                				else  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    122
                 | 
                                    
                                                     | 
                
                 | 
                					$fields .= sprintf("\t\t\t\$table->%s('%s')%s;" . PHP_EOL, $field->type->db, $field->name, $parsedModifiers); | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    123
                 | 
                                    
                                                     | 
                
                 | 
                			}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    124
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    125
                 | 
                                    
                                                     | 
                
                 | 
                			// Check foreign key  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    126
                 | 
                                    
                                                     | 
                
                 | 
                			if ($field->foreignKey)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    127
                 | 
                                    
                                                     | 
                
                 | 
                			{ | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    128
                 | 
                                    
                                                     | 
                
                 | 
                				$fields .= sprintf("\t\t\t\$table->foreign('%s')->references('%s')->on('%s');" . PHP_EOL . PHP_EOL, $field->name, $field->foreignKey->field, $field->foreignKey->table); | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    129
                 | 
                                    
                                                     | 
                
                 | 
                			}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    130
                 | 
                                    
                                                     | 
                
                 | 
                		}  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    131
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    132
                 | 
                                    
                                                     | 
                
                 | 
                		if($this->modelData->timeStamps)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    133
                 | 
                                    
                                                     | 
                
                 | 
                			$fields .= PHP_EOL . "\t\t\t\$table->timestamps();" . PHP_EOL;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    134
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    135
                 | 
                                    
                                                     | 
                
                 | 
                		$this->stub = str_replace('{{fields}}', $fields, $this->stub); | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    136
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    137
                 | 
                                    
                                                     | 
                
                 | 
                		return $this;  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
                | 
                    138
                 | 
                                    
                                                     | 
                
                 | 
                	}  | 
            
            
                                                        
            
                                    
            
            
                | 
                    139
                 | 
                                    
                                                     | 
                
                 | 
                }  | 
            
            
                        
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.