login form yii2 without database

i am trying to create simple Login form basic with yii2. But my code inactive

public function actionLogin()
{
    if (isset($_GET['submit'])) {
        if (!isset($_REQUEST["username"]) || empty($_REQUEST["username"]) ||
            !isset($_REQUEST["password"]) || empty($_REQUEST["password"])) {
            echo "Error";
            return;
        }

        $username = $_REQUEST["username"];
        $password = $_REQUEST["password"];

        // $user = Users::getData($username, $password);

        if ($username == 'admin' && $password == 'admin') {
            echo "Success";
            return;
        }
    }
}
<!DOCTYPE html >
<html>

<form action="" method="">

    User Name <input type="text" name="username">
    <br> 
    Password <input type="password" name="password"></input> 
    <br> 
    <input type="submit" value="Submit" name="submit"/>

</form>


</html>