including html menu links with php

Dear Experts,

I include a php file as a html menu which has only links on it.

<?php  include'menu.php';  ?>

My menu is like below. it has only html code inside with no head tags. 

<a href="firstpage.php"><button class="button button2">Öğüşl</button></a>
<a href="secondpage.php"><button class="button button2">Bşçle Ğşç</button></a>
<a href="thirdpage.php"><button class="button button2">ağçörv çğşr</button></a>

Select allOpen in new window

but some characters doesn't show up as they suppose to be shown on the page.
how can I make the menu.php page utf-8 so that the characters show up correctly?