Session data not being passed through to the next page - php

Question

I have a login system that has two pages, it's quite simple but it doesn't appear that the data is being passed through as I am being redirected back. I have tried a couple solutions. Adding exit; and die; after the inital redirect from the login. I have also printed the session_id which worked fine.
Login page:
session_start();
if(isset($_POST['login'])){
$username = strip_tags($_POST['username']);
$password = strip_tags($_POST['password']);
$username = stripslashes($username);
$password = stripslashes($password);
$password = md5($password);
$sql = "SELECT * FROM table WHERE username = :username LIMIT 1";
$stmt = $conn->prepare($sql);
$stmt->bindParam(":username", $username);
$stmt->execute();
foreach($stmt as $row) {
$id = $row['id'];
$db_password = $row['password'];
}
if($password == $db_password){
$_SESSION['username'] = $username;
$_SESSION['id'] = $id;
header("Location: admin.php");
exit;
}else{
echo "You did not enter the correct details.";
}
}
This is the admin page. It just redirects back to login and doesn't get any further down the page
session_start();
if(!isset($_SESSION['id'])){
header("Location: login.php");
}

Answer 1

execute()
Returns TRUE on success or FALSE on failure.
You need to fetch data form result set as
$stmt->execute();
$row = $stmt->fetch(PDO::FETCH_ASSOC);// fetch data
$id = $row['id'];
$db_password = $row['password'];
if($password == $db_password){// then compair
$_SESSION['username'] = $username;
$_SESSION['id'] = $id;
header("Location: admin.php");
exit;
}else{
echo "You did not enter the correct details.";
}