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<?php |
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/** |
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* BaconPdf |
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* |
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* @link http://github.com/Bacon/BaconPdf For the canonical source repository |
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* @copyright 2015 Ben Scholzen (DASPRiD) |
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* @license http://opensource.org/licenses/BSD-2-Clause Simplified BSD License |
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*/ |
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namespace Bacon\Pdf\Options; |
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use Bacon\Pdf\Encryption\AbstractEncryption; |
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use Bacon\Pdf\Encryption\NullEncryption; |
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use Bacon\Pdf\Exception\DomainException; |
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final class PdfWriterOptions |
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{ |
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/** |
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* @var string |
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*/ |
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private $pdfVersion; |
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/** |
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* @var EncryptionOptions|null |
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*/ |
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private $encryptionOptions; |
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/** |
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* @param string $pdfVersion |
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* @throws DomainException |
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*/ |
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public function __construct($pdfVersion = '1.7') |
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{ |
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if (!in_array($pdfVersion, ['1.3', '1.4', '1.5', '1.6', '1.7'])) { |
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throw new DomainException('PDF version is not in the supported range (1.3 - 1.7)'); |
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} |
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$this->pdfVersion = $pdfVersion; |
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} |
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/** |
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* Returns the PDF version to use for the document. |
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* |
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* @return string |
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*/ |
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public function getPdfVersion() |
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{ |
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return $this->pdfVersion; |
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} |
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/** |
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* Sets encryption options. |
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* |
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* @param EncryptionOptions $encryptionOptions |
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*/ |
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public function setEncryptionOptions(EncryptionOptions $encryptionOptions) |
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{ |
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$this->encryptionOptions = $encryptionOptions; |
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} |
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/** |
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* @param string $permanentFileIdentifier |
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* @return NullEncryption |
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*/ |
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public function getEncryption($permanentFileIdentifier) |
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{ |
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if (null === $this->encryptionOptions) { |
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return new NullEncryption(); |
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} |
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return AbstractEncryption::forPdfVersion($this->pdfVersion, $permanentFileIdentifier, $this->encryptionOptions); |
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} |
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} |
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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_function
expects aPost
object, and outputs the author of the post. The base classPost
returns a simple string and outputting a simple string will work just fine. However, the child classBlogPost
which is a sub-type ofPost
instead decided to return anobject
, and is therefore violating the SOLID principles. If aBlogPost
were passed tomy_function
, PHP would not complain, but ultimately fail when executing thestrtoupper
call in its body.