how to check function's execution?

hello I have a problem to check whether a function successfully inject to database or not, here is the code : if($object->dbupdate())

      echo 'done';
    else
       echo 'damn!';
inside the 'if' statement $obj->dbupdate() doesn't execute , how can I execute and check if it was a successful inject within this function? is it even possible or should I check within class or something?