checkdate

/**
* Function to check if a given date actually exists / is valid
* 
* @param strin|int $date
* 
* @return boolean 
*/
public function checkDate($date = null) {
    // Check if date is given
    if(isset($date) && $date != "") {
        // Check if given date is numeric
        if(is_numeric($date)) {
            return checkdate(date('m', $date), date('d', $date), date('Y', $date));
        }
 
        // Match the format of the date (YYYY-MM-DD YYYY/MM/DD YYYY.MM.DD)
        if(preg_match ("/^([0-9]{4})[-\.\/]{1}([0-9]{1,2})[-\.\/]{1}([0-9]{1,2})$/", $date, $parts)) {
            // Check weather the date is valid of not
            if(checkdate($parts[2],$parts[3],$parts[1])) {
                return true;
            } else {
                return false;
            }
        // Match the format of the date (DD-MM-YYYY DD/MM/YYYY DD.MM.YYYY)
        } elseif(preg_match ("/^([0-9]{1,2})[-\.\/]{1}([0-9]{1,2})[-\.\/]{1}([0-9]{4})$/", $date, $parts)) {
            if(checkdate($parts[2],$parts[1],$parts[3])) {
                return true;
            } else {
                return false;
            }
        }
    }
 
    return false;
}