filtering DOM elements in PHP

<?php
// http://stackoverflow.com/questions/17769436/how-to-delete-my-image-host-is-not
$a="<img src='myhost.com/img.jpg'/><img src='hosta.com/img.jpg'/><img src='http://hostb.com/img.jpg'/><img src='hostc.com/img.jpg'/>";
$myhost='myhost.com';
$doc = new DOMDocument('1.0'); //http://www.php.net/manual/en/class.domdocument.php#domdocument.props.documentelement
$doc->loadHTML($a);
$images = $doc->getElementsByTagName('img');
$regex = '§([\w]+://)?(\www\d*\.)?(.*)§i'; // http://www.php.net/manual/en/regexp.introduction.php
$domElemsToRemove = array();
foreach ($images as $image) {
  $src = $image->getAttribute('src');
  preg_match($regex,$src,$m);
  //if ($m[1]=='') { $m[1] = 'http://'; } //optional
  //var_export($m);
  $pos = strpos($m[3], $myhost);
  if ($pos === false || $pos>0) {
     $domElemsToRemove[] = $image;
  }
}
foreach( $domElemsToRemove as $domElement ){
  $domElement->parentNode->removeChild($domElement); // http://www.php.net/manual/en/domnode.removechild.php#90292
}
$result = $doc->saveHTML();
echo $result; // `<img src="myhost.com/img.jpg">`
?>