PHP GET没有价值

I have a little trouble wih getting the page=? value and use that value to retrieve content according to the correct page. Currently this code just keeps getting stuck at the home page, even whenever I try to open something as the " Languages " tab.

Would love some help..

<?php
session_start();

if( isset( $_GET["page"]) ) {
    $_SESSION["activePage"] = $_GET["page"];
}

if( !isset( $_GET["activePage"] ) ) {
    $_SESSION["activePage"] = "home";
}

?>

This is my PHP code

<div id="cs_menu">
        <ul class="ul_menu">
            <li><a href="?page=home">Home</a></li>

            <li><a href="?page=languages">Languages</a>
                <ul>
                    <li><a href="?page=dutch">Dutch</a></li>
                    <li><a href="?page=german">German</a></li>
                    <li><a href="?page=french">French</a></li>
                    <li><a href="?page=spanish">Spanish</a></li>
                </ul>
            </li>
            <li><a href="&page=dialecten">Dialecten</a>
                <ul>
                    <li><a href="?page=twents">Twents</a></li>
                    <li><a href="?page=fries">Fries</a></li>
                    <li><a href="?page=zachteg">Zachte G</a></li>
                    <li><a href="?page=rotterdams">Rotterdams</a></li>
                    <li><a href="?page=amsterdams">Amsterdams</a></li>
                </ul>
            </li>
            <li><a href="?page=provincies">Provincies</a>
                <ul>
                    <li><a href="?page=overijssel">Overijssel</a></li>
                    <li><a href="?page=noordholland">Noord-Holland</a></li>
                    <li><a href="?page=gelderland">Gelderland</a></li>
                </ul>
            </li>
        </ul>
    </div>

This is my HTML menu

<div id="content">

    <?php
        echo $_SESSION["activePage"];
        include "includes/".$_SESSION["activePage"].".phtml";
    ?>

</div>

Here I am calling the content

issue with $_GET parameter

 <?php
 session_start();

    if( isset( $_GET["page"]) ) {
    $_SESSION["activePage"] = $_GET["page"];
 }

 if( !isset( $_GET["page"] ) ) {
    $_SESSION["activePage"] = "home";
 }

?>

Mentioin Full url in href. As you gave href="?page=twents" it will try to open "?page=twents" and will get stuck.