如何在php中包含多个模板

I am learning my way around php applying some Separation of Concerns. I am at localhost/admin/index.php.

I have my index.php as follows

...
$admin = new Admin();
if($_SESSION["user_privilege"]!=100) {
    header("Location: error.php");
    exit;
}

else 

include('views/admin_panel.php');

'admin_panel.php'

 !DOCTYPE html> 
<html>
    <head>
        <title> Admin Panel </title>
    </head>
    <body>
    <?php
    /** Create an array of admin features with the key being the get url
        * and the value being the feature 
        */
        $tasks  = array('user_accounts'=> 'User account Management','products'   => 'Product management','categories' => 'Category Management','static_pages'=>'Page creation and deletion', 'customer_query'=> 'Answer Queries from users');

            echo '<ul>';
            foreach($tasks as $key => $val) {

                echo '<li><a href="index.php?'.$key.'">'.$val.'</a></li>';

                }
            echo '</ul>';

            ?>
    </body>
</html>

That's simple stuff. Now, if I have a GET request to, say index.php?user_accounts, and I have that template at 'views/user_accounts.php', I've added the following lines to index.php

if ($admin->clickAction("user_accounts") == true)
            include('views/user_accounts.php');
#The functions are defined in the model

But, is this the right way to do it? I guess not, because the previously included admin_panel also appears with the user_accounts template which is not what I was hoping for.