599 lines
18 KiB
PHP
599 lines
18 KiB
PHP
<?php
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/**
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* Class HTML_To_Markdown
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*
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* A helper class to convert HTML to Markdown.
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*
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* @version 2.2.1
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* @author Nick Cernis <nick@cern.is>
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* @link https://github.com/nickcernis/html2markdown/ Latest version on GitHub.
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* @link http://twitter.com/nickcernis Nick on twitter.
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* @license http://www.opensource.org/licenses/mit-license.php MIT
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*/
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class HTML_To_Markdown
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{
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/**
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* @var DOMDocument The root of the document tree that holds our HTML.
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*/
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private $document;
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/**
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* @var string|boolean The Markdown version of the original HTML, or false if conversion failed
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*/
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private $output;
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/**
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* @var array Class-wide options users can override.
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*/
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private $options = array(
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'header_style' => 'setext', // Set to "atx" to output H1 and H2 headers as # Header1 and ## Header2
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'suppress_errors' => true, // Set to false to show warnings when loading malformed HTML
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'strip_tags' => false, // Set to true to strip tags that don't have markdown equivalents. N.B. Strips tags, not their content. Useful to clean MS Word HTML output.
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'bold_style' => '**', // Set to '__' if you prefer the underlined style
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'italic_style' => '*', // Set to '_' if you prefer the underlined style
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'remove_nodes' => '', // space-separated list of dom nodes that should be removed. example: "meta style script"
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);
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/**
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* Constructor
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*
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* Set up a new DOMDocument from the supplied HTML, convert it to Markdown, and store it in $this->$output.
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*
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* @param string $html The HTML to convert to Markdown.
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* @param array $overrides [optional] List of style and error display overrides.
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*/
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public function __construct($html = null, $overrides = null)
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{
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if ($overrides)
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$this->options = array_merge($this->options, $overrides);
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if ($html)
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$this->convert($html);
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}
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/**
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* Setter for conversion options
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*
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* @param $name
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* @param $value
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*/
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public function set_option($name, $value)
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{
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$this->options[$name] = $value;
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}
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/**
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* Convert
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*
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* Loads HTML and passes to get_markdown()
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*
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* @param $html
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* @return string The Markdown version of the html
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*/
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public function convert($html)
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{
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$html = preg_replace('~>\s+<~', '><', $html); // Strip white space between tags to prevent creation of empty #text nodes
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$this->document = new DOMDocument();
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if ($this->options['suppress_errors'])
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libxml_use_internal_errors(true); // Suppress conversion errors (from http://bit.ly/pCCRSX )
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$this->document->loadHTML('<?xml encoding="UTF-8">' . $html); // Hack to load utf-8 HTML (from http://bit.ly/pVDyCt )
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$this->document->encoding = 'UTF-8';
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if ($this->options['suppress_errors'])
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libxml_clear_errors();
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return $this->get_markdown($html);
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}
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/**
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* Is Child Of?
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*
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* Is the node a child of the given parent tag?
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*
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* @param $parent_name string|array The name of the parent node(s) to search for e.g. 'code' or array('pre', 'code')
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* @param $node
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* @return bool
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*/
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private static function is_child_of($parent_name, $node)
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{
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for ($p = $node->parentNode; $p != false; $p = $p->parentNode) {
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if (is_null($p))
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return false;
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if ( is_array($parent_name) && in_array($p->nodeName, $parent_name) )
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return true;
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if ($p->nodeName == $parent_name)
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return true;
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}
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return false;
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}
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/**
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* Convert Children
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*
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* Recursive function to drill into the DOM and convert each node into Markdown from the inside out.
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*
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* Finds children of each node and convert those to #text nodes containing their Markdown equivalent,
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* starting with the innermost element and working up to the outermost element.
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*
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* @param $node
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*/
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private function convert_children($node)
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{
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// Don't convert HTML code inside <code> and <pre> blocks to Markdown - that should stay as HTML
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if (self::is_child_of(array('pre', 'code'), $node))
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return;
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// If the node has children, convert those to Markdown first
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if ($node->hasChildNodes()) {
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$length = $node->childNodes->length;
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for ($i = 0; $i < $length; $i++) {
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$child = $node->childNodes->item($i);
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$this->convert_children($child);
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}
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}
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// Now that child nodes have been converted, convert the original node
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$markdown = $this->convert_to_markdown($node);
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// Create a DOM text node containing the Markdown equivalent of the original node
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$markdown_node = $this->document->createTextNode($markdown);
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// Replace the old $node e.g. "<h3>Title</h3>" with the new $markdown_node e.g. "### Title"
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$node->parentNode->replaceChild($markdown_node, $node);
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}
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/**
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* Get Markdown
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*
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* Sends the body node to convert_children() to change inner nodes to Markdown #text nodes, then saves and
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* returns the resulting converted document as a string in Markdown format.
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*
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* @return string|boolean The converted HTML as Markdown, or false if conversion failed
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*/
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private function get_markdown()
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{
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// Work on the entire DOM tree (including head and body)
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$input = $this->document->getElementsByTagName("html")->item(0);
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if (!$input)
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return false;
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// Convert all children of this root element. The DOMDocument stored in $this->doc will
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// then consist of #text nodes, each containing a Markdown version of the original node
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// that it replaced.
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$this->convert_children($input);
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// Sanitize and return the body contents as a string.
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$markdown = $this->document->saveHTML(); // stores the DOMDocument as a string
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$markdown = html_entity_decode($markdown, ENT_QUOTES, 'UTF-8');
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$markdown = html_entity_decode($markdown, ENT_QUOTES, 'UTF-8'); // Double decode to cover cases like &nbsp; http://www.php.net/manual/en/function.htmlentities.php#99984
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$markdown = preg_replace("/<!DOCTYPE [^>]+>/", "", $markdown); // Strip doctype declaration
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$unwanted = array('<html>', '</html>', '<body>', '</body>', '<head>', '</head>', '<?xml encoding="UTF-8">', '
');
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$markdown = str_replace($unwanted, '', $markdown); // Strip unwanted tags
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$markdown = trim($markdown, "\n\r\0\x0B");
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$this->output = $markdown;
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return $markdown;
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}
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/**
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* Convert to Markdown
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*
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* Converts an individual node into a #text node containing a string of its Markdown equivalent.
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*
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* Example: An <h3> node with text content of "Title" becomes a text node with content of "### Title"
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*
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* @param $node
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* @return string The converted HTML as Markdown
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*/
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private function convert_to_markdown($node)
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{
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$tag = $node->nodeName; // the type of element, e.g. h1
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$value = $node->nodeValue; // the value of that element, e.g. The Title
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// Strip nodes named in remove_nodes
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$tags_to_remove = explode(' ', $this->options['remove_nodes']);
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if ( in_array($tag, $tags_to_remove) )
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return false;
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switch ($tag) {
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case "p":
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$markdown = (trim($value)) ? rtrim($value) . PHP_EOL . PHP_EOL : '';
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break;
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case "pre":
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$markdown = PHP_EOL . $this->convert_code($node) . PHP_EOL;
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break;
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case "h1":
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case "h2":
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$markdown = $this->convert_header($tag, $node);
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break;
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case "h3":
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$markdown = "### " . $value . PHP_EOL . PHP_EOL;
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break;
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case "h4":
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$markdown = "#### " . $value . PHP_EOL . PHP_EOL;
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break;
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case "h5":
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$markdown = "##### " . $value . PHP_EOL . PHP_EOL;
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break;
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case "h6":
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$markdown = "###### " . $value . PHP_EOL . PHP_EOL;
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break;
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case "em":
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case "i":
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case "strong":
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case "b":
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$markdown = $this->convert_emphasis($tag, $value);
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break;
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case "hr":
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$markdown = "- - - - - -" . PHP_EOL . PHP_EOL;
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break;
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case "br":
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$markdown = " " . PHP_EOL;
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break;
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case "blockquote":
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$markdown = $this->convert_blockquote($node);
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break;
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case "code":
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$markdown = $this->convert_code($node);
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break;
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case "ol":
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case "ul":
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$markdown = $value . PHP_EOL;
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break;
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case "li":
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$markdown = $this->convert_list($node);
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break;
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case "img":
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$markdown = $this->convert_image($node);
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break;
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case "a":
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$markdown = $this->convert_anchor($node);
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break;
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case "#text":
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$markdown = preg_replace('~\s+~', ' ', $value);
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$markdown = preg_replace('~^#~', '\\\\#', $markdown);
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break;
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case "#comment":
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$markdown = '';
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break;
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case "div":
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$markdown = ($this->options['strip_tags']) ? $value . PHP_EOL . PHP_EOL : html_entity_decode($node->C14N());
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break;
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default:
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// If strip_tags is false (the default), preserve tags that don't have Markdown equivalents,
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// such as <span> nodes on their own. C14N() canonicalizes the node to a string.
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// See: http://www.php.net/manual/en/domnode.c14n.php
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$markdown = ($this->options['strip_tags']) ? $value : html_entity_decode($node->C14N());
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}
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return $markdown;
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}
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/**
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* Convert Header
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*
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* Converts h1 and h2 headers to Markdown-style headers in setext style,
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* matching the number of underscores with the length of the title.
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*
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* e.g. Header 1 Header Two
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* ======== ----------
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*
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* Returns atx headers instead if $this->options['header_style'] is "atx"
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*
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* e.g. # Header 1 ## Header Two
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*
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* @param string $level The header level, including the "h". e.g. h1
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* @param string $node The node to convert.
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* @return string The Markdown version of the header.
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*/
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private function convert_header($level, $node)
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{
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$content = $node->nodeValue;
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if (!$this->is_child_of('blockquote', $node) && $this->options['header_style'] == "setext") {
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$length = (function_exists('mb_strlen')) ? mb_strlen($content, 'utf-8') : strlen($content);
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$underline = ($level == "h1") ? "=" : "-";
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$markdown = $content . PHP_EOL . str_repeat($underline, $length) . PHP_EOL . PHP_EOL; // setext style
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} else {
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$prefix = ($level == "h1") ? "# " : "## ";
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$markdown = $prefix . $content . PHP_EOL . PHP_EOL; // atx style
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}
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return $markdown;
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}
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/**
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* Converts inline styles
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* This function is used to render strong and em tags
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*
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* eg <strong>bold text</strong> becomes **bold text** or __bold text__
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*
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* @param string $tag
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* @param string $value
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* @return string
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*/
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private function convert_emphasis($tag, $value)
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{
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if ($tag == 'i' || $tag == 'em') {
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$markdown = $this->options['italic_style'] . $value . $this->options['italic_style'];
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} else {
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$markdown = $this->options['bold_style'] . $value . $this->options['bold_style'];
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}
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return $markdown;
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}
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/**
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* Convert Image
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*
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* Converts <img /> tags to Markdown.
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*
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* e.g. <img src="/path/img.jpg" alt="alt text" title="Title" />
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* becomes 
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*
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* @param $node
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* @return string
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*/
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private function convert_image($node)
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{
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$src = $node->getAttribute('src');
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$alt = $node->getAttribute('alt');
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$title = $node->getAttribute('title');
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if ($title != "") {
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$markdown = ''; // No newlines added. <img> should be in a block-level element.
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} else {
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$markdown = '';
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}
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return $markdown;
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}
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/**
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* Convert Anchor
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*
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* Converts <a> tags to Markdown.
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*
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* e.g. <a href="http://modernnerd.net" title="Title">Modern Nerd</a>
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* becomes [Modern Nerd](http://modernnerd.net "Title")
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*
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* @param $node
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* @return string
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*/
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private function convert_anchor($node)
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{
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$href = $node->getAttribute('href');
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$title = $node->getAttribute('title');
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$text = $node->nodeValue;
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if ($title != "") {
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$markdown = '[' . $text . '](' . $href . ' "' . $title . '")';
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} else {
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$markdown = '[' . $text . '](' . $href . ')';
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}
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if (! $href)
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$markdown = html_entity_decode($node->C14N());
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// Append a space if the node after this one is also an anchor
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$next_node_name = $this->get_next_node_name($node);
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if ($next_node_name == 'a')
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$markdown = $markdown . ' ';
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return $markdown;
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}
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/**
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* Convert List
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*
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* Converts <ul> and <ol> lists to Markdown.
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*
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* @param $node
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* @return string
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*/
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private function convert_list($node)
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{
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// If parent is an ol, use numbers, otherwise, use dashes
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$list_type = $node->parentNode->nodeName;
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$value = $node->nodeValue;
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if ($list_type == "ul") {
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$markdown = "- " . trim($value) . PHP_EOL;
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} else {
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$number = $this->get_position($node);
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$markdown = $number . ". " . trim($value) . PHP_EOL;
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}
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return $markdown;
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}
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/**
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* Convert Code
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*
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* Convert code tags by indenting blocks of code and wrapping single lines in backticks.
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*
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* @param DOMNode $node
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* @return string
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*/
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private function convert_code($node)
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{
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// Store the content of the code block in an array, one entry for each line
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$markdown = '';
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$code_content = html_entity_decode($node->C14N());
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$code_content = str_replace(array("<code>", "</code>"), "", $code_content);
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$code_content = str_replace(array("<pre>", "</pre>"), "", $code_content);
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$lines = preg_split('/\r\n|\r|\n/', $code_content);
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$total = count($lines);
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// If there's more than one line of code, prepend each line with four spaces and no backticks.
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if ($total > 1 || $node->nodeName === 'pre') {
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// Remove the first and last line if they're empty
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$first_line = trim($lines[0]);
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$last_line = trim($lines[$total - 1]);
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$first_line = trim($first_line, "
"); //trim XML style carriage returns too
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$last_line = trim($last_line, "
");
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if (empty($first_line))
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array_shift($lines);
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if (empty($last_line))
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array_pop($lines);
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$count = 1;
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foreach ($lines as $line) {
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$line = str_replace('
', '', $line);
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$markdown .= " " . $line;
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// Add newlines, except final line of the code
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if ($count != $total)
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$markdown .= PHP_EOL;
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$count++;
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}
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$markdown .= PHP_EOL;
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} else { // There's only one line of code. It's a code span, not a block. Just wrap it with backticks.
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$markdown .= "`" . $lines[0] . "`";
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}
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return $markdown;
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}
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/**
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* Convert blockquote
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*
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* Prepend blockquotes with > chars.
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*
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* @param $node
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* @return string
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*/
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private function convert_blockquote($node)
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{
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// Contents should have already been converted to Markdown by this point,
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// so we just need to add ">" symbols to each line.
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$markdown = '';
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$quote_content = trim($node->nodeValue);
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$lines = preg_split('/\r\n|\r|\n/', $quote_content);
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$total_lines = count($lines);
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foreach ($lines as $i => $line) {
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$markdown .= "> " . $line . PHP_EOL;
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if ($i + 1 == $total_lines)
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$markdown .= PHP_EOL;
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}
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return $markdown;
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}
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/**
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* Get Position
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*
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* Returns the numbered position of a node inside its parent
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*
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* @param $node
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* @return int The numbered position of the node, starting at 1.
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*/
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private function get_position($node)
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{
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// Get all of the nodes inside the parent
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$list_nodes = $node->parentNode->childNodes;
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$total_nodes = $list_nodes->length;
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$position = 1;
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// Loop through all nodes and find the given $node
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for ($a = 0; $a < $total_nodes; $a++) {
|
|
$current_node = $list_nodes->item($a);
|
|
|
|
if ($current_node->isSameNode($node))
|
|
$position = $a + 1;
|
|
}
|
|
|
|
return $position;
|
|
}
|
|
|
|
|
|
/**
|
|
* Get Next Node Name
|
|
*
|
|
* Return the name of the node immediately after the passed one.
|
|
*
|
|
* @param $node
|
|
* @return string|null The node name (e.g. 'h1') or null.
|
|
*/
|
|
private function get_next_node_name($node)
|
|
{
|
|
$next_node_name = null;
|
|
|
|
$current_position = $this->get_position($node);
|
|
$next_node = $node->parentNode->childNodes->item($current_position);
|
|
|
|
if ($next_node)
|
|
$next_node_name = $next_node->nodeName;
|
|
|
|
return $next_node_name;
|
|
}
|
|
|
|
|
|
/**
|
|
* To String
|
|
*
|
|
* Magic method to return Markdown output when HTML_To_Markdown instance is treated as a string.
|
|
*
|
|
* @return string
|
|
*/
|
|
public function __toString()
|
|
{
|
|
return $this->output();
|
|
}
|
|
|
|
|
|
/**
|
|
* Output
|
|
*
|
|
* Getter for the converted Markdown contents stored in $this->output
|
|
*
|
|
* @return string
|
|
*/
|
|
public function output()
|
|
{
|
|
if (!$this->output) {
|
|
return '';
|
|
} else {
|
|
return $this->output;
|
|
}
|
|
}
|
|
}
|