class customClass{
  function selfTest(){[..] return [message|false]}
}
class tester{
  function test($thing){
    if(is_object($thing)){
      if(method_exists($thing,'selfTest')){
        $this->handleTest(call_user_method('selfTest',$thing));
      }
    }else if(is_array($thing)){
      foreach($thing as $component){ $this->test($component); }
    }else{
    ;//ignore if not an array or object
    }
  }
  function handleTest($result){if($result)print "Warning $result";}
}

参考:
John.Wiley.and.Sons.PHP5.and.MySQL.Bible