| 1 |  |  | <?php | 
            
                                                                                                            
                            
            
                                    
            
            
                | 2 |  |  | /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 3 |  |  |  * BaconPdf | 
            
                                                                                                            
                            
            
                                    
            
            
                | 4 |  |  |  * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 5 |  |  |  * @link      http://github.com/Bacon/BaconPdf For the canonical source repository | 
            
                                                                                                            
                            
            
                                    
            
            
                | 6 |  |  |  * @copyright 2015 Ben Scholzen (DASPRiD) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 7 |  |  |  * @license   http://opensource.org/licenses/BSD-2-Clause Simplified BSD License | 
            
                                                                                                            
                            
            
                                    
            
            
                | 8 |  |  |  */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 9 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 10 |  |  | namespace Bacon\Pdf\Options; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 11 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 12 |  |  | use Bacon\Pdf\Encryption\AbstractEncryption; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 13 |  |  | use Bacon\Pdf\Encryption\NullEncryption; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 14 |  |  | use Bacon\Pdf\Exception\DomainException; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 15 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 16 |  |  | final class PdfWriterOptions | 
            
                                                                                                            
                            
            
                                    
            
            
                | 17 |  |  | { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 18 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 19 |  |  |      * @var string | 
            
                                                                                                            
                            
            
                                    
            
            
                | 20 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 21 |  |  |     private $pdfVersion; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 22 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 23 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 24 |  |  |      * @var EncryptionOptions|null | 
            
                                                                                                            
                            
            
                                    
            
            
                | 25 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 26 |  |  |     private $encryptionOptions; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 27 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 28 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 29 |  |  |      * @param  string $pdfVersion | 
            
                                                                                                            
                            
            
                                    
            
            
                | 30 |  |  |      * @throws DomainException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 31 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 32 |  |  |     public function __construct($pdfVersion = '1.7') | 
            
                                                                                                            
                            
            
                                    
            
            
                | 33 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 34 |  |  |         if (!in_array($pdfVersion, ['1.3', '1.4', '1.5', '1.6', '1.7'])) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 35 |  |  |             throw new DomainException('PDF version is not in the supported range (1.3 - 1.7)'); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 36 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 37 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 38 |  |  |         $this->pdfVersion = $pdfVersion; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 39 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 40 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 41 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 42 |  |  |      * Returns the PDF version to use for the document. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 43 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 44 |  |  |      * @return string | 
            
                                                                                                            
                            
            
                                    
            
            
                | 45 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 46 |  |  |     public function getPdfVersion() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 47 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 48 |  |  |         return $this->pdfVersion; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 49 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 50 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 51 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 52 |  |  |      * Sets encryption options. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 53 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 54 |  |  |      * @param EncryptionOptions $encryptionOptions | 
            
                                                                                                            
                            
            
                                    
            
            
                | 55 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 56 |  |  |     public function setEncryptionOptions(EncryptionOptions $encryptionOptions) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 57 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 58 |  |  |         $this->encryptionOptions = $encryptionOptions; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 59 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 60 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 61 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 62 |  |  |      * @param  string $permanentFileIdentifier | 
            
                                                                                                            
                            
            
                                    
            
            
                | 63 |  |  |      * @return NullEncryption | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 64 |  |  |      */ | 
            
                                                        
            
                                    
            
            
                | 65 |  |  |     public function getEncryption($permanentFileIdentifier) | 
            
                                                        
            
                                    
            
            
                | 66 |  |  |     { | 
            
                                                        
            
                                    
            
            
                | 67 |  |  |         if (null === $this->encryptionOptions) { | 
            
                                                        
            
                                    
            
            
                | 68 |  |  |             return new NullEncryption(); | 
            
                                                        
            
                                    
            
            
                | 69 |  |  |         } | 
            
                                                        
            
                                    
            
            
                | 70 |  |  |  | 
            
                                                        
            
                                    
            
            
                | 71 |  |  |         return AbstractEncryption::forPdfVersion($this->pdfVersion, $permanentFileIdentifier, $this->encryptionOptions); | 
                            
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                | 72 |  |  |     } | 
            
                                                        
            
                                    
            
            
                | 73 |  |  | } | 
            
                                                        
            
                                    
            
            
                | 74 |  |  |  | 
            
                        
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.