Something

function runExternal($cmd,&$code) {
   $descriptorspec = array(
	   0 => array("pipe", "r"),  // stdin is a pipe that the child will read from
	   1 => array("pipe", "w"),  // stdout is a pipe that the child will write to
	   2 => array("pipe", "w")   // stderr is a file to write to
   );
  
   $pipes= array();
   $process = proc_open($cmd, $descriptorspec, $pipes);
  
   $output= "";
  
   if (!is_resource($process)) return false;
  
   #close child's input imidiately
   fclose($pipes[0]);
  
   stream_set_blocking($pipes[1],false);
   stream_set_blocking($pipes[2],false);
  
   $todo= array($pipes[1],$pipes[2]);
  
   while( true ) {
	   $read= array();
	   if( !feof($pipes[1]) ) $read[]= $pipes[1];
	   if( !feof($pipes[2]) ) $read[]= $pipes[2];
	  
	   if (!$read) break;
	  
	   $ready= stream_select($read, $write=NULL, $ex= NULL, 2);
	  
	   if ($ready === false) {
		   break; #should never happen - something died
	   }
	  
	   foreach ($read as $r) {
		   $s= fread($r,1024);
		   $output.= $s;
	   }
   }
  
   fclose($pipes[1]);
   fclose($pipes[2]);
  
   $code= proc_close($process);
  
   return $output;
}