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<?php |
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/** |
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* Webino (http://webino.sk) |
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* |
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* @link https://github.com/webino/WebinoDraw for the canonical source repository |
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* @copyright Copyright (c) 2012-2016 Webino, s. r. o. (http://webino.sk) |
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* @author Peter Bačinský <[email protected]> |
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* @license BSD-3-Clause |
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*/ |
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namespace WebinoDraw\Dom; |
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use DOMXpath; |
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use WebinoDraw\Exception; |
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/** |
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* Extended DOMDocument |
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*/ |
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class Document extends \DOMDocument |
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{ |
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/** |
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* @var DOMXpath |
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*/ |
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protected $xpath; |
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/** |
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* @param string $version |
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* @param string $encoding |
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*/ |
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public function __construct($version = null, $encoding = null) |
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{ |
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parent::__construct($version, $encoding); |
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$this->registerNodeClass('DOMElement', Element::class); |
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$this->registerNodeClass('DOMText', Text::class); |
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$this->registerNodeClass('DOMAttr', Attr::class); |
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} |
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/** |
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* @return DOMXpath |
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*/ |
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public function getXpath() |
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{ |
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if (null == $this->xpath) { |
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$this->setXpath(new DOMXPath($this)); |
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} |
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return $this->xpath; |
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} |
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/** |
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* @param DOMXpath $xpath |
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* @return $this |
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*/ |
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public function setXpath(DOMXpath $xpath) |
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{ |
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$this->xpath = $xpath; |
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return $this; |
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} |
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/** |
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* @return Element |
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*/ |
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public function getDocumentElement() |
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{ |
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return $this->documentElement; |
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} |
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/** |
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* @param string $source |
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* @param array|null $options |
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* @return bool |
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*/ |
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public function loadHTML($source, $options = null) |
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{ |
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// hack HTML5 |
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$errors = libxml_use_internal_errors(); |
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libxml_use_internal_errors(true); |
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$markup = mb_convert_encoding($source, 'HTML-ENTITIES', 'UTF-8'); |
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$result = parent::loadHTML($markup, LIBXML_COMPACT | $options); |
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libxml_use_internal_errors($errors); |
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return $result; |
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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_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.