使用javascript和php的外部服务器html

I am unable to write external HTML using JavaScript.

Can anyone help me using php and JavaScript like this way.

<div id="include"></div>

in this i want to put HTML from another server.

<script type="text/javascript">
var a = "SRC='http://demoserver.com/read_files.php?f1=headermenu.html";
document.write ("<script type='text/javascript' "+a+"'>");
document.write("</scr"+"ipt>");

here is my php code on my server

<?php
    $url = 'http://demoserver.com/headermenu.html';
    $htm = file_get_contents($url);
    echo $htm;
?>

and html code is

<ul class="menu-link">
<li><a href="">Menu1</a></li>
<li><a href="">Menu2</a></li>
<li><a href="">Menu3</a></li>
<li><a href="">Menu4</a></li>
</ul>