function get_user_browser()
{
    $u_agent = $_SERVER['HTTP_USER_AGENT'];
    $ub = '';
    if(preg_match('/MSIE/i',$u_agent))
    {
        $ub = "ie";
    }
    elseif(preg_match('/Firefox/i',$u_agent))
    {
        $ub = "firefox";
    }
    elseif(preg_match('/Safari/i',$u_agent))
    {
        $ub = "safari";
    }
    elseif(preg_match('/Chrome/i',$u_agent))
    {
        $ub = "chrome";
    }
    elseif(preg_match('/Flock/i',$u_agent))
    {
        $ub = "flock";
    }
    elseif(preg_match('/Opera/i',$u_agent))
    {
        $ub = "opera";
    }
   
    return $ub;
}

if(get_user_browser()=="chrome"){
echo "Lütfen farklı bir browser ile giriş yapınız";
exit();
}