function hook_body($obj) 
{
   echo "<h1>START</h1>";   
   $doc = new DOMDocument();
   libxml_use_internal_errors(true);
   $doc->loadHTML($obj); // loads your html
   $xpath = new DOMXPath($doc);

   // select all pre tags with attributes
   $nodelist = $xpath->query("//pre[@*]");
   // iterate through selected nodes and print them
   for($i=0; $i < $nodelist->length; $i++) {
       $node = $nodelist->item($i);
       echo $node->nodeValue; //var_dump($node->nodeValue);
   }

   echo "<h1>END</h1>";
   echo $obj;
}