How to retrieve "profile_" only filelds? Now I load user profile fields of a $uid  by:

$thisuser = user_load(array('uid' =&gt; $uid));
profile_load_profile($thisuser);
drupal_json($thisuser);


Is there a quick way to filter only fields with leading profile_ in $thisuser and so drupal_json displays only profile values?
The condition should be preg_match("/^profile_/", $profile). Have look at preg_match.