Fatal error: Call to a member function getAttribute() on a non-object

For some reason I can pull out a DomElement object into a variable but try to access it's methods and I get the above error. Use it in the foreach and the DomElement object works just fine.

function pb_get_image($output){
      $doc = new DOMDocument();
	  @$doc->loadHTML($output);
	  $tags = $doc->getElementsByTagName('img');
	  /*
	  $tags = object(DOMNodeList)#244 (1) { ["length"]=> int(1) }  
	  */
	  $test = $doc->getElementsByTagName('img')->item(0);
	  /*
	  $test = object(DOMElement)#242 (17) { ["tagName"]=> string(3) "img" ["schemaTypeInfo"]=> .....
	  */

//	  $width = $test->getAttribute('height');
	  /* This returns:
	
Fatal error: Call to a member function getAttribute() on a non-object in D:sharedwpdeva01wp-contentthemespicturebloghome.php on line 38  */

	  echo "width = $width";
       echo '$tags =';
	   var_dump($tags);
	   echo '$test =';
	   var_dump($test);

	  foreach ($tags as $tag) {
	         echo ' $tag =';
			 var_dump($tag);
	/*
	tag = object(DOMElement)#242 (17) { ["tagName"]=> string(3) "img" ["schemaTypeInfo"]=> ...
	
	*/
	         $src = $tag->getAttribute('height'); //this works no problem!?!
             var_dump($src);
			 }
	  return $output;
}