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html2markdown.php
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html2markdown.php
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<?php
#
# html2markdown - An HTML-to-markdown conversion tool for PHP
# Copyright (c) 2011 Nick Cernis | @nickcernis | http://modnerd.com
#
# Version 1.0.1
# Latest version available from https://github.com/nickcernis/html2markdown/
#
# Licensed under The MIT license
# http://www.opensource.org/licenses/mit-license.php
#
# Requires PHP 5
#
## Settings ##
# Change to "ATX" to output H1 and H2 headers as #Header1 and ##Header2
# See http://daringfireball.net/projects/markdown/syntax#header
if (!defined('HTML2MD_HEADER_STYLE')) define('HTML2MD_HEADER_STYLE', 'SETEX');
# Change to false to show warnings when loading malformed HTML/unsupported tags
if (!defined('HTML2MD_SUPPRESS_ERRORS')) define('HTML2MD_SUPPRESS_ERRORS', true);
# New line in converted markdown result text
if (!defined('HTML2MD_NEWLINE')) define('HTML2MD_NEWLINE', "\r\n");
if (!function_exists('html2markdown')) {
function html2markdown($html) {
$parser = new HTML_Parser($html);
return $parser->get_markdown();
}
}
class HTML_Parser
{
public $doc;
//public $html;
public function __construct($html)
{
$html = preg_replace('~>\s+<~', '><', $html); # Strip white space between tags to ensure uniform output
$this->doc = new DOMDocument();
if (HTML2MD_SUPPRESS_ERRORS)
libxml_use_internal_errors(true); # Suppress conversion errors (from http://bit.ly/pCCRSX )
$this->doc->loadHTML('<?xml encoding="UTF-8">'.$html); # Hack to load utf-8 HTML (from http://bit.ly/pVDyCt )
$this->doc->encoding = 'UTF-8';
if (HTML2MD_SUPPRESS_ERRORS)
libxml_clear_errors();
}
# Don't convert code that's inside a code block
private static function has_parent_code($node) {
for ($p = $node->parentNode; $p != false; $p = $p->parentNode) {
if (is_null($p)) return false;
if ($p->nodeName == 'code') return true;
}
return false;
}
# Convert child nodes from the outside in
private function convert_children($node) {
if (self::has_parent_code($node)) return;
if ($node->hasChildNodes()) {
for ($length = $node->childNodes->length, $i = 0; $i < $length; $i++) {
$child = $node->childNodes->item($i);
$this->convert_children($child);
}
}
$this->convert_to_markdown($node);
}
public function get_markdown()
{
# Use the body tag as our root element
$body = $this->doc->getElementsByTagName("body")->item(0);
# For each element inside the body, find child elements and convert
# those to markdown #text nodes, starting with the innermost element
# and working towards the outermost element ($node).
$this->convert_children($body);
# The DOMDocument represented by $doc now consists of #text nodes, each containing a
# markdown version of the original DOM node created by convert_to_markdown().
# Return the <body> contents of $doc, first stripping html and body tags, the DOCTYPE
# and XML encoding lines, then converting entities such as & back to &.
$markdown = $this->doc->saveHTML();
// Double decode. http://www.php.net/manual/en/function.htmlentities.php#99984
$markdown = html_entity_decode($markdown, ENT_QUOTES, 'UTF-8');
$markdown = html_entity_decode($markdown, ENT_QUOTES, 'UTF-8');
$markdown = preg_replace("/<!DOCTYPE [^>]+>/", "", $markdown);
$remove = array('<html>','</html>','<body>','</body>', '<?xml encoding="UTF-8">', '
');
$markdown = str_replace($remove, '', $markdown);
return $markdown;
}
# Convert the supplied element into its markdown equivalent,
# then swap the original element in the DOM with the markdown
# version as a #text node. This converts the HTML $doc into
# markdown while retaining the nesting and order of all tags.
private function convert_to_markdown($node)
{
$tag = $node->nodeName; #the type of element, e.g. h1
$value = $node->nodeValue; #the value of that element, e.g. The Title
switch ($tag)
{
case "p":
case "pre":
$markdown = $value.HTML2MD_NEWLINE.HTML2MD_NEWLINE;
break;
case "h1":
$markdown = $this->convert_header("h1", $value);
break;
case "h2":
$markdown = $this->convert_header("h2", $value);
break;
case "h3":
$markdown = "### ".$value.HTML2MD_NEWLINE.HTML2MD_NEWLINE;
break;
case "h4":
$markdown = "#### ".$value.HTML2MD_NEWLINE.HTML2MD_NEWLINE;
break;
case "h5":
$markdown = "##### ".$value.HTML2MD_NEWLINE.HTML2MD_NEWLINE;
break;
case "h6":
$markdown = "###### ".$value.HTML2MD_NEWLINE.HTML2MD_NEWLINE;
break;
case "em":
case "i":
$markdown = "*".$value."*";
break;
case "strong":
case "b":
$markdown = "**".$value."**";
break;
case "hr":
$markdown = "- - - - - -".HTML2MD_NEWLINE.HTML2MD_NEWLINE;
break;
case "br":
$markdown = " " . HTML2MD_NEWLINE;
break;
case "blockquote":
$markdown = $this->convert_blockquote($node);
break;
case "code":
$markdown = $this->convert_code($node);
break;
case "ol":
case "ul":
$markdown = $value . HTML2MD_NEWLINE;
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;
default:
# Preserve tags that don't have markdown equivalents, such as <span>
# and #text nodes on their own, like WordPress [short_tags].
# C14N() is the XML canonicalization function (undocumented).
# It returns the full content of the node, including surrounding tags.
$markdown = $node->C14N();
}
#Create a DOM text node containing the markdown equivalent of the original node
$markdown_node = $this->doc->createTextNode($markdown);
#Swap the old $node e.g. <h3>Title</h3> with the new $markdown_node e.g. ###Title
$node->parentNode->replaceChild($markdown_node, $node);
}
# Converts h1 and h2 headers to markdown-style headers in setex style,
# matching the number of underscores with the length of the title.
#
# e.g. Header 1 Header Two
# ======== ----------
#
# Returns atx headers instead if HTML2MD_HEADER_STYLE is "ATX"
#
# e.g. #Header 1 ##Header Two
#
private function convert_header($level, $content)
{
if (HTML2MD_HEADER_STYLE == "SETEX")
{
$length = (function_exists('mb_strlen')) ? mb_strlen($content, 'utf-8') : strlen($content);
$underline = ($level == "h1") ? "=" : "-";
$markdown = $content. HTML2MD_NEWLINE .str_repeat($underline, $length). HTML2MD_NEWLINE . HTML2MD_NEWLINE; #Setex style
} else {
$prefix = ($level == "h1") ? "# " : "## ";
$markdown = $prefix.$content. HTML2MD_NEWLINE . HTML2MD_NEWLINE; #atx style
}
return $markdown;
}
# Converts <img /> tags to markdown
#
# e.g. <img src="/path/img.jpg" alt="blah" title="Title" />
#
# becomes 
#
private function convert_image($node)
{
$src = $node->getAttribute('src');
$alt = $node->getAttribute('alt');
$title = $node->getAttribute('title');
if ($title != ""){
$markdown = ''; # No newlines added. <img> should be in a block-level element.
} else {
$markdown = '';
}
return $markdown;
}
# Converts <a> tags to markdown
#
# e.g. <a href="http://modnerd.com" title="Title">Modern Nerd</a>
#
# becomes [Modern Nerd](http://modnerd.com "Title")
#
private function convert_anchor($node)
{
$href = $node->getAttribute('href');
$title = $node->getAttribute('title');
$text = $node->nodeValue;
if ($title != ""){
$markdown = '['.$text.']('.$href.' "'.$title.'")';
} else {
$markdown = '['.$text.']('.$href.')';
}
return $markdown;
}
private function convert_list($node)
{
#If parent is an ol, use numbers, otherwise, use dashes
$list_type = $node->parentNode->nodeName;
$value = $node->nodeValue;
if ($list_type == "ul"){
$markdown = "- ".$value.HTML2MD_NEWLINE;
} else {
$number = $this->get_list_position($node);
$markdown = $number.". ".$value.HTML2MD_NEWLINE;
}
return $markdown;
}
private function convert_code($node)
{
# Store the content of the code block in an array, one entry for each line
$markdown = '';
$code_content = $node->C14N();
$code_content = str_replace(array("<code>","</code>"), 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){
# 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 = trim($line, '
');
$line = str_replace('
', '', $line);
$markdown .= " ".$line;
// Add newlines, except final line of the code
if ($count != $total) $markdown .= HTML2MD_NEWLINE;
$count++;
}
$markdown .= HTML2MD_NEWLINE;
$markdown = html_entity_decode($markdown, ENT_QUOTES, 'UTF-8');
} 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 $markdown;
}
private function convert_blockquote($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 );
$lines = array_filter($lines); //strips empty lines
foreach($lines as $line){
$markdown .= "> ".$line. HTML2MD_NEWLINE . HTML2MD_NEWLINE;
}
return $markdown;
}
#
# Helper methods
#
# Returns numbered position of an <li> inside an <ol>
private function get_list_position($node)
{
# Get all of the li nodes inside the parent
$list_nodes = $node->parentNode->childNodes;
$total_nodes = $list_nodes->length;
$position = 1;
# Loop through all li nodes and find the one we passed
for ($a = 0; $a < $total_nodes; $a++)
{
$current_node = $list_nodes->item($a);
if ($current_node->isSameNode($node))
$position = $a + 1;
}
return $position;
}
}