- var_dump: documentation ( source)
- preg_match: documentation ( source)
- implode: documentation ( source)
- range: documentation ( source)
<?php
$date = "4/23/15";
echo $x = '~^(?:' . implode('|', range(1, 12)) . ')\/(?:' . implode('|', range(1, 31)) . ')\/[0-9]{2}$~';
preg_match($x, $date, $m);
var_dump($m);