HTML absolutizer

absolutize.php

<?php

  function absolutize($html, $base) {
    //  href, src, background attributes
    $html = preg_replace('#(<[^>]+(href|src|background)=(?:3D)?")(?![a-z]+:)/?([^"]+)"#is', '$1'.$base.'$3"', $html);
    //  style attributes url(), src()
    $html = preg_replace('#(<[^>]+style=(?:3D)?"[^"]*(url|src)\([\s\']*)(?![a-z]+:)/?([^)]+)\)#is', '$1'.$base.'$3)', $html);
    
    //  style tag
    preg_match_all('#<style[^>]*>([^<]+)#is', $html, $styles);
    foreach($styles[1] as $style){
      $html = str_replace(
        $style, 
        preg_replace('#((url|src)\([\s\']*)(?![a-z]+:)/?([^)]+)\)#is', '$1'.$base.'$3)',  $style),
        $html);
    };
    
    return  $html;
  }

?>