- preg_match: documentation ( source)
<?php
$startDate = '2014-01-01';
$endDate = '2014-12-31';
$pattern = '/^(\d{4})-(\d{2})-(\d{2})$/';
if (!preg_match($pattern, $startDate) || !preg_match($pattern, $endDate)) {
echo 'Invalid date ranges';
} else {
echo 'GTG!';
}