php template engine pure

// method render template engine
function templates($content, $data = array(), $return = false)
    {

        foreach($data as $key => $value)
            $$key = $value;

        $content = array('template/header','template/topnav', $content, 'template/footer');

        ob_start();

        include 'template/header.php';

        $template = ob_get_contents();

        ob_end_flush();

        var_dump($template);

        if($return)
            echo $template;
        else
            return $template;
    }

//logic request utk render
    function login()
    {
        $this->templates('view/login');
    }

//bentuk html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- The above 3 meta tags *must* come first in the head; any other head content must come *after* these tags -->
    <title><?= $label_app_name ?></title>       <======== <$label_app_name undefined>

    <!-- Bootstrap -->
    <link href="<?= asset_url('css/font-awesome.min.css') ?>" rel="stylesheet">

    <link href="<?= asset_url('css/bootstrap.min.css') ?>" rel="stylesheet">

    <link href="<?= asset_url('css/navbar.css') ?>" rel="stylesheet">

//data yg mau dikirim
return array(
    'label_app_name'    => "AntonSby",
    'label_app_copyright'   =>  "Dashboard &copy; 2019",

    'label_btn_login'   =>  "Login",
    'label_input_user'  =>  "User",
    'label_input_pass'  =>  "Password",
);