if (isset($_GET["btn"])) // the name of submit is "btn"
 {
    if (!empty($_GET["name"]) && !empty($_GET["lname"])) {
        $name = $_GET["name"] ;
        $lname = $_GET["lname"] ;
        echo "your name is $name and your lastname is $lname" ;
    }else {
        echo "fill in the blanks!!" ;
    }
}
?>