session ในการเปลี่ยนภาษาไม่ยอมเก็บค่าครับ รวบกวนผู้รู้ช่วยดูให้หน่อย

<?php
@ob_start();
@session_start();
if($_GET["lang"] != "" && $_GET["lang"] == "th")
{
	$_SESSION["lang"] = "th";
}
elseif($_GET["lang"] != "" && $_GET["lang"] == "en")
{
	$_SESSION["lang"] = "en";
}
elseif($_GET["lang"] != "" && $_GET["lang"] == "jp")
{
	$_SESSION["lang"] = "jp";
}
else
{
	$_SESSION["lang"] = session_id();
}
echo $_SESSION["lang"];
?>

<?php session_start();
if(isset($_GET["lang"]) && $_GET["lang"] != ""){
	$_SESSION["lang"] = $_GET["lang"];
}
?>