Use a language dropdown selector to use a GET function to change language

Question

Hi I'm trying to use a dropdown selector to change the language of my wordpress website I'm designing, I used a simple setlanguage(); function that I did in php But the selected option on the html code won't change the url to affect the site. Is there a solution I can use to do that?

What I've tried

I've tried to add a onChange="window.location.href=this.value" to the html also i've tried to add some javascrip

<script type="text/javascript">
  var urlmenu = document.getElementById( 'menu1' );
  urlmenu.onchange = function() {
       window.open( this.options[ this.selectedIndex ].value );
  };
</script>

This is the dropdown html I've been [using][1] http://www.ixtendo.com/polyglot-language-switcher-jquery-plugin/

here is a [demo][2] http://www.ixtendo.com/demo/polyglot-language-switcher-jquery-plugin-2.2/index.html

The php function I've used to change the language

<?php
 function setlanguage()
 {
   if (isset($_GET['lan'])) 
   {
     if($_GET['lan'] == 'en')
     {
       require_once('php/languages/en.php');
     }else{ 
       require_once('php/languages/al.php');
    }
  }
   else{ 
     require_once('php/languages/al.php');
   }
}
setlanguage();
?>