get yesterday date in php

how to get date of yesterday using php   <?php $test=date(‘d.m.Y’,strtotime(“-1 days”)); echo $test; ?> or <?php $test=date(‘d-m-Y’,strtotime(“-1 days”)); echo $test; ?> or <?php $test=date(‘y-m-d’,strtotime(“-1 days”)); echo $test; ?>