ขอความ Ajax login อยากกำหนดสิทธิ์ระดับการเข้าใช้งานครับ

<?php
session_start();
include_once("db.php");
if(isset($_POST['login_button'])) {
	$user_email = trim($_POST['user_email']);
	$user_password = trim($_POST['password']);

	$sql = "SELECT aid, user, pass, email , rule FROM admin_system WHERE email='$user_email'";
	$resultset = mysqli_query($conn, $sql) or die("database error:". mysqli_error($conn));
	$row = mysqli_fetch_assoc($resultset);

	if($row['pass']==$user_password){
		echo "ok";
		$_SESSION['user_session'] = $row['aid'];
	
	} else {
		echo "email or password does not exist."; // wrong details
	}
}



?>

$('document').ready(function() {
	/* handling form validation */
	$("#login-form").validate({
		rules: {
			password: {
				required: true,
			},
			user_email: {
				required: true,
				email: true
			},
		},
		messages: {
			password:{
			  required: "<div class='text-danger'>  please enter your password </div>"
			 },
			user_email: "  <div class='text-danger'> please enter your email address </div>",
		},
		submitHandler: submitForm
	});
	/* Handling login functionality */
	function submitForm() {
		var data = $("#login-form").serialize();
		$.ajax({
			type : 'POST',
			url  : 'login.php',
			data : data,
			beforeSend: function(){
				$("#error").fadeOut();
				$("#login_button").html('<i class="icon-spinner9 spinner mr-2"></i> &nbsp; sending ...');
			},
			success : function(response){
				if(response=="ok"){
					$("#login_button").html('<i class="icon-spinner9 spinner mr-2"></i> &nbsp; Signing In ...');
					setTimeout(' window.location.href = "welcome.php"; ',4000);
				} else {
					$("#error").fadeIn(1000, function(){
						$("#error").html('<div class="alert alert-warning border-0 alert-dismissible">  &nbsp; '+response+' !</div>');
						$("#login_button").html('<span class="glyphicon glyphicon-log-in"></span> &nbsp; Sign In');
					});
				}
			}
		});
		return false;
	}
});