/**
 * The function is_date() validates the date and returns true or false
 * @param $str sting expected valid date format
 * @return bool returns true if the supplied parameter is a valid date
 * otherwise false
 */
function is_date( $str ) {
    try {
        $dt = new DateTime( trim($str) );
    }
    catch( Exception $e ) {
        return false;
    }
    $month = $dt->format('m');
    $day = $dt->format('d');
    $year = $dt->format('Y');
    if( checkdate($month, $day, $year) ) {
        return true;
    }
    else {
        return false;
    }
}