* @link https://github.com/nickcernis/html2markdown/ Latest version on GitHub. * @link http://twitter.com/nickcernis Nick on twitter. * @license http://www.opensource.org/licenses/mit-license.php MIT */ class HTML_To_Markdown { /** * @var DOMDocument The root of the document tree that holds our HTML. */ private $document; /** * @var string|boolean The Markdown version of the original HTML, or false if conversion failed */ private $output; /** * @var array Class-wide options users can override. */ private $options = array( 'header_style' => 'setext', // Set to "atx" to output H1 and H2 headers as # Header1 and ## Header2 'suppress_errors' => true, // Set to false to show warnings when loading malformed HTML '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. 'bold_style' => '**', // Set to '__' if you prefer the underlined style 'italic_style' => '*', // Set to '_' if you prefer the underlined style 'remove_nodes' => '', // space-separated list of dom nodes that should be removed. example: "meta style script" ); /** * Constructor * * Set up a new DOMDocument from the supplied HTML, convert it to Markdown, and store it in $this->$output. * * @param string $html The HTML to convert to Markdown. * @param array $overrides [optional] List of style and error display overrides. */ public function __construct($html = null, $overrides = null) { if ($overrides) $this->options = array_merge($this->options, $overrides); if ($html) $this->convert($html); } /** * Setter for conversion options * * @param $name * @param $value */ public function set_option($name, $value) { $this->options[$name] = $value; } /** * Convert * * Loads HTML and passes to get_markdown() * * @param $html * @return string The Markdown version of the html */ public function convert($html) { $html = preg_replace('~>\s+<~', '><', $html); // Strip white space between tags to prevent creation of empty #text nodes $this->document = new DOMDocument(); if ($this->options['suppress_errors']) libxml_use_internal_errors(true); // Suppress conversion errors (from http://bit.ly/pCCRSX ) $this->document->loadHTML('' . $html); // Hack to load utf-8 HTML (from http://bit.ly/pVDyCt ) $this->document->encoding = 'UTF-8'; if ($this->options['suppress_errors']) libxml_clear_errors(); return $this->get_markdown($html); } /** * Is Child Of? * * Is the node a child of the given parent tag? * * @param $parent_name string The name of the parent node to search for (e.g. 'code') * @param $node * @return bool */ private static function is_child_of($parent_name, $node) { for ($p = $node->parentNode; $p != false; $p = $p->parentNode) { if (is_null($p)) return false; if ($p->nodeName == $parent_name) return true; } return false; } /** * Convert Children * * Recursive function to drill into the DOM and convert each node into Markdown from the inside out. * * Finds children of each node and convert those to #text nodes containing their Markdown equivalent, * starting with the innermost element and working up to the outermost element. * * @param $node */ private function convert_children($node) { // Don't convert HTML code inside and
 blocks to Markdown - that should stay as HTML
        if (self::is_child_of('pre', $node) || self::is_child_of('code', $node))
            return;

        // If the node has children, convert those to Markdown first
        if ($node->hasChildNodes()) {
            $length = $node->childNodes->length;

            for ($i = 0; $i < $length; $i++) {
                $child = $node->childNodes->item($i);
                $this->convert_children($child);
            }
        }

        // Now that child nodes have been converted, convert the original node
        $markdown = $this->convert_to_markdown($node);

        // Create a DOM text node containing the Markdown equivalent of the original node
        $markdown_node = $this->document->createTextNode($markdown);

        // Replace the old $node e.g. "

Title

" with the new $markdown_node e.g. "### Title" $node->parentNode->replaceChild($markdown_node, $node); } /** * Get Markdown * * Sends the body node to convert_children() to change inner nodes to Markdown #text nodes, then saves and * returns the resulting converted document as a string in Markdown format. * * @return string|boolean The converted HTML as Markdown, or false if conversion failed */ private function get_markdown() { // Work on the entire DOM tree (including head and body) $input = $this->document->getElementsByTagName("html")->item(0); if (!$input) return false; // Convert all children of this root element. The DOMDocument stored in $this->doc will // then consist of #text nodes, each containing a Markdown version of the original node // that it replaced. $this->convert_children($input); // Sanitize and return the body contents as a string. $markdown = $this->document->saveHTML(); // stores the DOMDocument as a string $markdown = html_entity_decode($markdown, ENT_QUOTES, 'UTF-8'); $markdown = html_entity_decode($markdown, ENT_QUOTES, 'UTF-8'); // Double decode to cover cases like &nbsp; http://www.php.net/manual/en/function.htmlentities.php#99984 $markdown = preg_replace("/]+>/", "", $markdown); // Strip doctype declaration $unwanted = array('', '', '', '', '', '', '', ' '); $markdown = str_replace($unwanted, '', $markdown); // Strip unwanted tags $markdown = trim($markdown, "\n\r\0\x0B"); $this->output = $markdown; return $markdown; } /** * Convert to Markdown * * Converts an individual node into a #text node containing a string of its Markdown equivalent. * * Example: An

node with text content of "Title" becomes a text node with content of "### Title" * * @param $node * @return string The converted HTML as Markdown */ private function convert_to_markdown($node) { $tag = $node->nodeName; // the type of element, e.g. h1 $value = $node->nodeValue; // the value of that element, e.g. The Title // Strip nodes named in remove_nodes $tags_to_remove = explode(' ', $this->options['remove_nodes']); if ( in_array($tag, $tags_to_remove) ) return false; switch ($tag) { case "p": $markdown = (trim($value)) ? rtrim($value) . PHP_EOL . PHP_EOL : ''; break; case "pre": $markdown = PHP_EOL . $this->convert_code($node) . PHP_EOL; break; case "h1": case "h2": $markdown = $this->convert_header($tag, $node); break; case "h3": $markdown = "### " . $value . PHP_EOL . PHP_EOL; break; case "h4": $markdown = "#### " . $value . PHP_EOL . PHP_EOL; break; case "h5": $markdown = "##### " . $value . PHP_EOL . PHP_EOL; break; case "h6": $markdown = "###### " . $value . PHP_EOL . PHP_EOL; break; case "em": case "i": case "strong": case "b": $markdown = $this->convert_emphasis($tag, $value); break; case "hr": $markdown = "- - - - - -" . PHP_EOL . PHP_EOL; break; case "br": $markdown = " " . PHP_EOL; break; case "blockquote": $markdown = $this->convert_blockquote($node); break; case "code": $markdown = $this->convert_code($node); break; case "ol": case "ul": $markdown = $value . PHP_EOL; break; case "li": $markdown = $this->convert_list($node); break; case "img": $markdown = $this->convert_image($node); break; case "a": $markdown = $this->convert_anchor($node); break; case "#text": $markdown = preg_replace('~\s+~', ' ', $value); $markdown = preg_replace('~^#~', '\\\\#', $markdown); break; case "#comment": $markdown = ''; break; case "div": $markdown = ($this->options['strip_tags']) ? $value . PHP_EOL . PHP_EOL : html_entity_decode($node->C14N()); break; default: // If strip_tags is false (the default), preserve tags that don't have Markdown equivalents, // such as nodes on their own. C14N() canonicalizes the node to a string. // See: http://www.php.net/manual/en/domnode.c14n.php $markdown = ($this->options['strip_tags']) ? $value : html_entity_decode($node->C14N()); } return $markdown; } /** * Convert Header * * Converts h1 and h2 headers to Markdown-style headers in setext style, * matching the number of underscores with the length of the title. * * e.g. Header 1 Header Two * ======== ---------- * * Returns atx headers instead if $this->options['header_style'] is "atx" * * e.g. # Header 1 ## Header Two * * @param string $level The header level, including the "h". e.g. h1 * @param string $node The node to convert. * @return string The Markdown version of the header. */ private function convert_header($level, $node) { $content = $node->nodeValue; if (!$this->is_child_of('blockquote', $node) && $this->options['header_style'] == "setext") { $length = (function_exists('mb_strlen')) ? mb_strlen($content, 'utf-8') : strlen($content); $underline = ($level == "h1") ? "=" : "-"; $markdown = $content . PHP_EOL . str_repeat($underline, $length) . PHP_EOL . PHP_EOL; // setext style } else { $prefix = ($level == "h1") ? "# " : "## "; $markdown = $prefix . $content . PHP_EOL . PHP_EOL; // atx style } return $markdown; } /** * Converts inline styles * This function is used to render strong and em tags * * eg bold text becomes **bold text** or __bold text__ * * @param string $tag * @param string $value * @return string */ private function convert_emphasis($tag, $value) { if ($tag == 'i' || $tag == 'em') { $markdown = $this->options['italic_style'] . $value . $this->options['italic_style']; } else { $markdown = $this->options['bold_style'] . $value . $this->options['bold_style']; } return $markdown; } /** * Convert Image * * Converts tags to Markdown. * * e.g. alt text * becomes ![alt text](/path/img.jpg "Title") * * @param $node * @return string */ private function convert_image($node) { $src = $node->getAttribute('src'); $alt = $node->getAttribute('alt'); $title = $node->getAttribute('title'); if ($title != "") { $markdown = '![' . $alt . '](' . $src . ' "' . $title . '")'; // No newlines added. should be in a block-level element. } else { $markdown = '![' . $alt . '](' . $src . ')'; } return $markdown; } /** * Convert Anchor * * Converts tags to Markdown. * * e.g. Modern Nerd * becomes [Modern Nerd](http://modernnerd.net "Title") * * @param $node * @return string */ private function convert_anchor($node) { $href = $node->getAttribute('href'); $title = $node->getAttribute('title'); $text = $node->nodeValue; if ($title != "") { $markdown = '[' . $text . '](' . $href . ' "' . $title . '")'; } else { $markdown = '[' . $text . '](' . $href . ')'; } // Append a space if the node after this one is also an anchor $next_node_name = $this->get_next_node_name($node); if ($next_node_name == 'a') $markdown = $markdown . ' '; return $markdown; } /** * Convert List * * Converts
    and
      lists to Markdown. * * @param $node * @return string */ private function convert_list($node) { // If parent is an ol, use numbers, otherwise, use dashes $list_type = $node->parentNode->nodeName; $value = $node->nodeValue; if ($list_type == "ul") { $markdown = "- " . trim($value) . PHP_EOL; } else { $number = $this->get_position($node); $markdown = $number . ". " . trim($value) . PHP_EOL; } return $markdown; } /** * Convert Code * * Convert code tags by indenting blocks of code and wrapping single lines in backticks. * * @param DOMNode $node * @return string */ private function convert_code($node) { // Store the content of the code block in an array, one entry for each line $markdown = ''; $code_content = html_entity_decode($this->document->saveHTML($node)); $code_content = str_replace(array("", ""), "", $code_content); $code_content = str_replace(array("
      ", "
      "), "", $code_content); $lines = preg_split('/\r\n|\r|\n/', $code_content); $total = count($lines); // If there's more than one line of code, prepend each line with four spaces and no backticks. if ($total > 1 || $node->nodeName === 'pre') { // Remove the first and last line if they're empty $first_line = trim($lines[0]); $last_line = trim($lines[$total - 1]); $first_line = trim($first_line, " "); //trim XML style carriage returns too $last_line = trim($last_line, " "); if (empty($first_line)) array_shift($lines); if (empty($last_line)) array_pop($lines); $count = 1; foreach ($lines as $line) { $line = str_replace(' ', '', $line); $markdown .= " " . $line; // Add newlines, except final line of the code if ($count != $total) $markdown .= PHP_EOL; $count++; } $markdown .= PHP_EOL; } else { // There's only one line of code. It's a code span, not a block. Just wrap it with backticks. $markdown .= "`" . $lines[0] . "`"; } return $markdown; } /** * Convert blockquote * * Prepend blockquotes with > chars. * * @param $node * @return string */ private function convert_blockquote($node) { // Contents should have already been converted to Markdown by this point, // so we just need to add ">" symbols to each line. $markdown = ''; $quote_content = trim($node->nodeValue); $lines = preg_split('/\r\n|\r|\n/', $quote_content); $total_lines = count($lines); foreach ($lines as $i => $line) { $markdown .= "> " . $line . PHP_EOL; if ($i + 1 == $total_lines) $markdown .= PHP_EOL; } return $markdown; } /** * Get Position * * Returns the numbered position of a node inside its parent * * @param $node * @return int The numbered position of the node, starting at 1. */ private function get_position($node) { // Get all of the nodes inside the parent $list_nodes = $node->parentNode->childNodes; $total_nodes = $list_nodes->length; $position = 1; // Loop through all nodes and find the given $node for ($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; } } }