How to use the date function in php?

[Bleh22]

The function is working properly, except that it always returns the same date even if I pass different values.
It always returns the same date it was set to. How can I fix it?

function convertDate($month,$day,$year) {
$form_date = $month . ' ' . $day . ', ' . $year;
$mysql_date = date('Y-m-d', strtotime($form_date));
return $mysql_date;
}