การทำ from logig ด้วย php กับฐานข้อมูล oracle

<?
$user_login=$_POST[user];
$pass_login=$_POST[password];
if($user_login=="" or $pass_login=="") {

exit();
}
include "connect.php";

$query = "SELECT * from tb_admin where ADMIN_LOGIN ='$user_login' and ADMIN_PASSWORD='$pass_login'";
$statement = oci_parse ($connection, $query);
$row=oci_execute ($statement);

if($num<=0) {
echo"รหัสไม่ถูกต้อง";
} else {
session_start();
$_SESSION[sess_userid]=session_id();
$_SESSION[sess_username]=$user_login;
header("Location:menu.php");
}
?>