Snippit: PHP: Simple US Zip Code format validation

gistfile1.php

<?php
/* Validates if $zipCode is a 5 digit number in the 12345 format. Note that this simply checks to see if $zipCode is a 5 digit number, not necessarily a valid U.S. Zip Code.
*/
function validateZipCode($zipCode) {
if (preg_match('#[0-9]{5}#', $zipCode))
	return true;
else
	return false;
}
?>

what bout to add empty zipcode