ensure_YYMMDD_FI.php

<?php
function correctYYMMDD($input){
	$input = substr($input, 0, 6);
	
	//is it already in correct format?
	if(preg_match('/[0-9][0-9](1[0-2]|0[1-9])([0-2][0-9]|3[01])/', $input)) return $input;
	
	//let's reverse it.
	$rev = array();
	$rev['yy'] = substr($input, 4, 2);
	$rev['mm'] = substr($input, 2, 2);
	$rev['dd'] = substr($input, 0, 2);
	
	return $rev['yy'].$rev['mm'].$rev['dd'];
}
?>