How to use Codeigniter GET parameters with UTF-8 like Arabic characters

When i send a GET data in codeigniter in arabic i obtain nothing in GET array, i set the character header utf-8 in the top of the html tags but the problem persists. For example when i send a value as الأسبانى for $_GET[‘nom’] parameter i receive nothing like is shown in the profiler below :

GET DATA  
$_GET['nom']  
$_GET['ville']  
$_GET['specialite']  
$_GET['submit']   Chercher ...

…

Bu, when i specify the character code utf-8,i receive ASCII code this:

GET DATA  
$_GET['nom']  

$_GET['ville']  
$_GET['specialite']  
$_GET['submit']   Chercher ...

So, instead of الأسبانى i have  "157&# 5;&# 16 "


Someone had an idea about that issue, thanks in advance