/**
* Poor man's age limit validation
* Due to the lack of simple and exact PHP time diff function,
* we conveniently forget leap years
*/
function ageLimit( $data, $reqAge ) {
    $date = strtotime( $data['birthday'] );
    if( $date !== false && $date !== -1 ) { // strtotime returns -1 < PHP 5.1.0
        $diff = time() - $date;
        return ( $diff / 31556926 > $reqAge ); // 31556926 seconds in a year
    }
    return false; // date malformed
}

http://bin.cakephp.org/view/1184217660

Cake PHP age validation

PHP