extract image source attribute from html string in Drupal

template.php

/**
* Author: ihsanberahim
* Author Url: http://blog.powergeng.com
* Author Facebook: http://facebook.com/ihsanberahim
*
* i found it from stackoverflow
*/

function content2src($html){
  $doc = new DOMDocument();
  libxml_use_internal_errors(true);
  $doc->loadHTML( $html );
  $xpath = new DOMXPath($doc);
  $imgs = $xpath->query("//img");
  for ($i=0; $i < $imgs->length; $i++) {
      $img = $imgs->item($i);
      $src = $img->getAttribute("src");
  }

  return $src;
}