Check Date is valid

isValidDate.php

/**
 * @param string $date
 * @param string $format
 * @return boolean
 */
public function isValidDate($date, $format = 'dd.mm.yyyy') {
    if (strlen($date) >= 6 && strlen($format) == 10) {

        // find separator. Remove all other characters from $format 
        $separator_only = str_replace(array('m', 'd', 'y'), '', $format);
        $separator = $separator_only[0]; // separator is first character 

        if ($separator) {
            $arr = explode($separator, $date);
            $day = $arr[0];
            $month = $arr[1];
            $year = $arr[2];

            if (checkdate($month, $day, $year))
                return true;
        }
    }
    return false;
}