PHP $_SESSION variable undefined using Slim - php

Question

I'm trying to set a session variable in php using Slim. I want the users id to be stored as a variable to use elsewhere. I think I have the syntax or order wrong in my functions.
Here is my function to set the variable:
function loadAdmin()
{
//Set new session and save user id to variable
if (!isset($_SESSION)) {
session_start();
}
$app = \Slim\Slim::getInstance();
$token = $app->request->headers->get('token');
$token_exists = getToken_Validate();
if($token_exists) {
$sql = "SELECT id, title AS admin_title, last_name AS admin_last_name
FROM admin WHERE token=:token";
try {
$db = getDB();
$stmt = $db->prepare($sql);
$stmt->bindValue(':token', $token);
$stmt->execute();
$admin = $stmt->fetchAll(PDO::FETCH_OBJ);
$db = null;
echo json_encode($admin);
$_SESSION['uid'] = $stmt['id'];
} catch(PDOException $e) {
echo '{"error":{"text":'. $e->getMessage() .'}}';
}
} else {
echo '{"err": "failed"}';
}
}
Here is my function to use the variable when fetching specific data:
function loadDashboard()
{
session_start();
$uid = $_SESSION['uid'];
$token_exists = getToken_Validate();
if ($token_exists) {
//Get number of rows from multiple tables
$sql = "SELECT
(SELECT COUNT(*) FROM users WHERE id=:uid) AS total_students,
(SELECT COUNT(*) FROM subjects) AS total_subjects,
(SELECT COUNT(*) FROM notes) AS total_notes";
try {
$db = getDB();
$stmt = $db->prepare($sql);
$stmt->bindValue(':uid', $uid);
$stmt->execute();
$users = $stmt->fetchAll(PDO::FETCH_OBJ);
$db = null;
echo json_encode($users);
} catch(PDOException $e) {
echo '{"error":{"text":'. $e->getMessage() .'}}';
}
} else {
echo '{"err": "failed"}';
}
}
The Slim error I get after trying to loadDashboard is:
Undefined index: uid
Sorry if my PHP is awful, any help is appreciated.

Answer 1

Turns out it had nothing to do with Slim.
$_SESSION['uid'] = $stmt['id']; was not storing anything to the variable.
I had to first bind the id column to a variable:
$stmt->bindColumn('id', $uid);
Then I could set that variable as a session variable:
$_SESSION['uid'] = $uid;
Here is the full working function:
function loadAdmin()
{
if (!isset($_SESSION)) {
session_start();
}
$app = \Slim\Slim::getInstance();
$token = $app->request->headers->get('token');
$token_exists = getToken_Validate();
if($token_exists) {
$sql = "SELECT
id,
title AS admin_title,
last_name AS admin_last_name
FROM admin WHERE token=:token";
try {
$db = getDB();
$stmt = $db->prepare($sql);
$stmt->bindValue(':token', $token);
$stmt->execute();
$stmt->bindColumn('id', $uid);
$admin = $stmt->fetchAll(PDO::FETCH_OBJ);
$db = null;
$_SESSION['uid'] = $uid;
echo json_encode($admin);
}
catch(PDOException $e) {
echo '{"error":{"text":'. $e->getMessage() .'}}';
}
}
else {
echo '{"err": "failed"}';
}
}