get last month php

$currentMonth = date('M');// if number, then date('m');
//Last month
$lastMonth = Date("F", strtotime("first day of previous month");
$nextMonth = Date("F", strtotime("first day of next month");

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

//Last month
$lastMonth = Date("F", strtotime("first day of previous month");
$nextMonth = Date("F", strtotime("first day of next month");