php get end date of month

<?php

$query_date = '2010-02-04';

// First day of the month.
echo date('Y-m-01', strtotime($query_date));

// Last day of the month.
echo date('Y-m-t', strtotime($query_date));

$a_date = "2009-11-23";
echo date("Y-m-t", strtotime($a_date));