- date: documentation ( source)
- strtotime: documentation ( source)
<?php
echo date('Y-m-d H:i:s', strtotime('this Monday midnight', strtotime('2014-07-14')));
echo date('Y-m-d H:i:s', strtotime('this Monday midnight', strtotime('2014-07-15')));
echo date('Y-m-d H:i:s', strtotime('next Monday midnight', strtotime('2014-07-14')));
echo date('Y-m-d H:i:s', strtotime('next Monday midnight', strtotime('2014-07-15')));