get previous month first date in php code example

Example 1: get next month first day php

$config_month  = 1;
$config_day = 1;

$new_expiry_date = date('Y-m-d', mktime(0, 0, 0, date('m') + $config_month, 1 + $config_day, date('Y')));

Example 2: php date function get previous month

$tgl = '25 january 2012';

$prevmonth = date("M Y",mktime(0,0,0,date("m", strtotime($tgl))-1,1,date("Y", strtotime($tgl))));
echo $prevmonth;