How to add some flag to the ext/Filter?

Hi All I am a beginner to PHP extension. And I want to add a flag named "FILTER_FLAG_STRIP_WHITESP", and associate this flag with FILTER_UNSAFE_RAW so that the ext/filter will auto trim $_GET/$_POST/$_REQUEST using the default filter.. At present, we should trim these data using code like this: <?php function trim_value(&$value){ $value = trim($value); } array_walk_recursive($_POST,'trim_value'); ?> I think we can do this job with less code, and get better performance with ext/filter. But I don't know how to do this work. Would any one please tell me how to? thank you. Best Reguards, -- Chi-BiN Hsiao