Restricting access to an admin page through sessions - php

Question

I've been stuck trying to block access to an admin page using PHP. The PHP is below but I can't figure out which combination of statement I need to use for the permission to be selected.
When I dump my session it's always null but the email session is there. It's a simple login requiring email and password. I basically want it to also get their permission from the DB.
<?php
session_start();
include ('../config/config.php');
/* basic field validation */
$email = trim($_POST["email"]);
$password = trim ($_POST["password"]);
/* check if details are empty, redirect if they are */
if (empty($email) or empty($password)) {
$_SESSION["message"] = "You must enter your email and password";
//Redirect to index
header("Location: ../index.php");
exit;
}
/* sanitise the input */
$email = strip_tags($email);
$password = strip_tags($password);
/* SQL user selection query, with error handling for the SQL */
$query = "SELECT email, permission FROM users WHERE email = '$email' AND password = '$password'";
$result = mysqli_query($mysqli,$query) or exit("Error in query: $query. " . mysqli_error());
/* on query success, set sessions for email and userid */
if ($row = mysqli_fetch_assoc($result)) {
$_SESSION["authemail"] = $email;
$_SESSION["permission"] = $permission;
/* redirect the user to the secured page */
header("Location: ../loggedin.php");
} else {
/* display error if login was not successful and redirect to index */
$_SESSION["message"] = "Could not log in as $email - $query";
header("index.php");
}
?>
Feel free to edit some of the text out if it isn't relavent.