<?php
$current_month = date('m');
$current_quarter_start = ceil($current_month/4)*3+1; // get the starting month of the current quarter
echo $start_date = date("Y-m-d H:i:s", mktime(0, 0, 0, $current_quarter_start, 1, date('Y') ));
echo $end_date = date("Y-m-d H:i:s", mktime(0, 0, 0, $current_quarter_start+3, 1, date('Y') ));
// by adding or subtracting from $current_quarter_start within the mktime function you can get any quarter of any year you want.
// return array($start_date, $end_date);
// print_r($months);