_POST, foreach, strip_tags

[MacWorks]

Thanks for taking a look at this:

I'm currently cleaning up $_POST vars like this:

if ( is_array( $POST ))
   {
      foreach ( $POST as $key => $value )
         {
            $post_vars[ trim(strip_tags( $key )) ] = trim(strip_tags( $value ));
         }
   }

THE QUESTION:

I'm wondering if there's a malicious code risk in the foreach statement. Could I do it like this to avoid that risk:

if ( is_array( $POST ))
   {
      foreach ( $POST as trim(strip_tags( $key )) => trim(strip_tags( $value )))
         {
            $post_vars[ $key ] = $value;
         }
   }

Can I turn on a PHP option to automatically strip_tags from $POST, $GET, $_COOKIES ?? I'm running PHP 4.3.3.

Thanks for any help,
Christopher