[HTML2Markdown] HTML to Markdown converter #php #function #markdown

html2markdown.php

<?php

/* ------------------------------------------------------------------- */
/* [HTML2Markdown] HTML to Markdown converter #PHP #function #markdown */
/* ------------------------------------------------------------------- */
  
$html = '
<h1>Headline 1</h1>
<h2>Headline 2</h2>
<h3>Headline 3</h3>
<h4>Headline 4</h4>
<h5>Headline 5</h5>
<h6>Headline 6</h6>
<hr>
<strong>Strong</strong><br />
<b>Bold</b><br />
<hr>
<em>Emphasized</em><br />
<i>Italic</i><br />
<hr>
<table style="width:100%">
<tr>
  <th>Name</th>
  <th style="color:red">Telephone</th>
</tr>
<tr>
  <td>Bill Gates</td>
  <td>55577855</td>
</tr>
<tr>
  <td>John Dow</td>
  <td>5557720</td>
</tr>
</table>
<hr>
<ul>
 <li> Dog </li>
 <li> Cat </li>
 <li> Mouse </li>
</ul>
<hr>
<ol>
  <li> Mike </li>
  <li> John </li>
  <li> Chris </li>
</ol>
<hr>
<blockquote>
"Design is the intermediary between information and understanding."
<br>
Richard Grefé, Designstratege
</blockquote>
<hr>
<img src="https://picsum.photos/seed/picsum/1024/100" alt="Lorem Picsum" title="Image">
<hr>
<a target="_blank" href="https://www.example.com/">www.example.com</a>';

#$html = file_get_contents('http://www.example.com/');

echo '<xmp>'.html2markdown($html); // TO TEST PASTE RESULT HERE https://dillinger.io/

/*
 * to-markdown - an HTML to Markdown converter for PHP
 *
 * Copyright 2013, Blake Turner
 * Improved 2020, Igor Gaffling
 * Licenced under the MIT licence
 *
 */

function html2markdown($string, $clean_up=TRUE, $tidy_up=TRUE) {
  // INI
  $markdown = $string;
  // USE ONLY THE BODY OF A WEBPAGE
  if ($clean_up == TRUE) {
    // CORRECT THE HTML - or use https://www.barattalo.it/html-fixer/
    $dom = new DOMDocument(); // FIX ENCODING https://stackoverflow.com/a/8218649
    @$dom->loadHTML(mb_convert_encoding($markdown, 'HTML-ENTITIES', 'UTF-8'));
    $markdown = $dom->saveHTML();
    // preg_match() IS NOT SO NICE, BUT WORKS FOR ME
    preg_match("/<body[^>]*>(.*?)<\/body>/is", $markdown, $matches);
    $markdown = $matches[1];
    $markdown = str_replace(array("\r","\n","\t",'  '), array('','','',' '), $markdown);
  }
  // GET RID OF ATTRIBUTES! PARTICULARLY USEFUL WHEN CONVERTING GARBAGE WYSIWYG CODE TO MARKDOWN
  if ($tidy_up == TRUE) {
    $elements = array(
      'table', 'tr', 'th', 'td', 
      'ul', 'ol', 'li',
      'p', 'blockquote',
      'strong', 'b', 'em', 'i', 'hr',
      'h1', 'h2', 'h3', 'h4', 'h5', 'h6'
    );
    foreach ($elements as $element) {
      $markdown = preg_replace("/<$element .*?>/", "<$element>", $markdown);
    }
  }
  // REPLACE SIMPLE TAGS WITH MARKDOWN EQUIVALENT
  $regexMap = array(
    'p'         => '',
    '\/p'       => PHP_EOL,
    'span'      => '',
    'span.*?'   => '',
    '\/span'    => '',
    'div'       => '',
    'div.*?'    => '',
    '\/div'     => '',
    'h1'        => '# ',
    'h2'        => '## ',
    'h3'        => '### ',
    'h4'        => '#### ',
    'h5'        => '##### ',
    'h6'        => '###### ',
    '\/h\d'     => PHP_EOL,
    'br'        => PHP_EOL,
    'br\s\/'    => PHP_EOL,
    'hr'        => PHP_EOL.'---'.PHP_EOL.PHP_EOL,
    'hr.*?'     => PHP_EOL.'---'.PHP_EOL.PHP_EOL,
    'strong'    => '__',
    '\/strong'  => '__',
    'b'         => '__',
    '\/b'       => '__',
    'em'        => '_',
    '\/em'      => '_',
    'i'         => '_',
    '\/i'       => '_',
  );
  foreach ($regexMap as $el => $replacement) {
    $markdown = preg_replace("/\<$el\>/i", $replacement, $markdown);
  }
  // IMAGES
  if (preg_match_all('/<img.*src="([^\s"]*?)".*>?/i', $markdown, $matches)) {
    foreach ($matches[0] as $i => $img_markup) {
      $url = $matches[1][$i];
      $alt = '';
      if (preg_match('/alt="([^"]*?)"/i', $img_markup, $alt_match)) {
        $alt = $alt_match[1];
      }
      if ($alt == '' and preg_match('/title="([^"]*?)"/i', $img_markup, $alt_match)) {
        $alt = $alt_match[1];
      }
      $img_markdown = '!['.$alt.']('.$url.')';
      $markdown = str_replace($img_markup, $img_markdown, $markdown);
    }
  }
  // LINKS
  if (preg_match_all('/<a.*?href="([^\s"]*?)".*?>(.*?)?<\/a>/is', $markdown, $matches)) {
    foreach ($matches[0] as $i => $a_markup) {
      $href = $matches[1][$i];
      $text = $matches[2][$i];
      $a_markdown = '['.$text.']('.$href.')';
      $markdown = str_replace($a_markup, $a_markdown, $markdown);
    }
  }
  // UNORDERED LISTS
  if (preg_match_all('/<ul>(.*?)<\/ul>/is', $markdown, $ul_matches)) {
    $markdown = preg_replace('/<ul>|<\/ul>/i', '', $markdown);
    foreach ($ul_matches[0] as $ul) {
      if (preg_match_all('/[\t ]?<li>(.*?)<\/li>/is', $ul, $list_items_ul)) {
        foreach ($list_items_ul[0] as $i => $ulli_markup) {
          $ulli_inner = trim($list_items_ul[1][$i]);
          $ulli_markdown = ' * ' . $ulli_inner.PHP_EOL;
          $markdown = str_replace($ulli_markup, $ulli_markdown, $markdown);
        }
      }
    }
  }
  // ORDERED LISTS
  if (preg_match_all('/<ol>(.*?)<\/ol>/is', $markdown, $ol_matches)) {
    $markdown = preg_replace('/<ol>|<\/ol>/i', '', $markdown);
    foreach ($ol_matches[0] as $ol) {
      if (preg_match_all('/[\t ]?<li>(.*?)<\/li>/is', $ol, $list_items_ol)) {
        foreach ($list_items_ol[0] as $i => $olli_markup) {
          $olli_inner = trim($list_items_ol[1][$i]);
          $olli_markdown = ' ' . ($i+1) . '. ' . $olli_inner.PHP_EOL;
          $markdown = str_replace($olli_markup, $olli_markdown, $markdown);
        }
      }
    }
  }
  // TABLE
  if (preg_match_all('/<table>(.*?)<\/table>/s', $markdown, $matches)) {
    $markdown = preg_replace('/<table>|<\/table>/', '', $markdown);
    foreach ($matches[0] as $table) {
      if (preg_match_all('/<tr>(.*?)<\/tr>/s', $table, $table_items)) {
        foreach ($table_items[0] as $i => $tr_markup) {
          if (preg_match_all('/.*?<(th|td)>(.*?)<\/(th|td)>.*?/s', $tr_markup, $tr_items)) {
            $colums = count($tr_items[1]);
            foreach ($tr_items[0] as $i => $tr_markup) {
              $td_inner = $tr_items[2][$i];
              $td_markdown = $td_inner;
              if ($colums!=($i+1)) $td_markdown = '|'.$td_inner.'|';
              $markdown = str_replace($tr_markup, $td_markdown, $markdown);
            }
          }
        }
      }
    }
    $head = PHP_EOL.'|'.str_repeat('---|', $colums).PHP_EOL;
    $markdown = preg_replace('/<\/tr>/', '|'.$head, $markdown, 1);
    $markdown = preg_replace('/<\/tr>/', '|'.PHP_EOL, $markdown);
  }
  // BLOCKQUOTES
  if (preg_match_all('/<blockquote>(.*?)<\/blockquote>/is', $markdown, $matches)) {  
    $blockquote_markdown = '';
    foreach ($matches[1] as $i => $inner_html) {
      $blockquote_markup = $matches[$i];
      $blockquote_markdown = '';
      $lines = explode(PHP_EOL, $inner_html);
      foreach ($lines as $line) {
        $blockquote_markdown .= '> ' . $line . PHP_EOL;
      }
      $markdown = str_replace($blockquote_markup, $blockquote_markdown, $markdown);
    }
  }
  return trim($markdown);
}