- date: documentation ( source)
- strtotime: documentation ( source)
- sprintf: documentation ( source)
<?php
$fromDate = '25-11-2013';
$fromDate = sprintf('%d-%d-%d', $d, $m, $Y);
$strFromDate = date("Y-m-d", strtotime("$Y-$m-$d"));
echo $strFromDate; // 2018-05-06