PDO user id session

class User {
	public $uid = "";

	public function userInfo($user_id) {
		global $db;

		$query = $db->prepare("SELECT `user_id`, `username`, `email` FROM `users` WHERE `user_id` = :id");
		$query->bindValue(':id', $user_id);
		$query->execute();

		return $query->fetch();
	}

	public function login($login, $password){
		global $db;

		$query = $db->prepare("SELECT COUNT(*) FROM `users` WHERE `username` = :user AND `password` = :pass OR `email` = :user AND `password` = :pass");
		
		$query->bindValue(':user', $login);
		$query->bindValue(':pass', $password);
		$query->execute();
		
		$result = (bool) $query->fetchColumn(0);

		if($result) {
			$this->uid = $result['user_id'];
		} 

		return $result;
	}

}

Login

<?php
if (isset($_POST['login'], $_POST['password'])) {

	$login = $_POST['login'];
	$password = sha1($_POST['password']);
	
	$errors = array();

	if (empty($login) || empty($password))
	{
	 $errors[] = 'All fields required!';
	} 
	else {

		$user = new User;
		$log_in = $user->login($login, $password); 
			if ($log_in) 
			{ 
				$_SESSION['user_id'] = $user->uid; 
				header('Location: account.php');
				exit();

			} else { 
				$errors[] = 'Username/Email or password incorrect!';
			}
	}
	
	if (!empty($errors)){
		
			foreach ($errors as $error)
			{
				echo '<div id="error"><strong>', $error, '</strong></div><br />';
			}
		}
}
?>

Account page

$user_id = $_SESSION['user_id'];
$user = new User;
$data = $user->userInfo($user_id);
echo $data['username'],'<br />';
echo $data['email'],'<br />';

echo '<pre>';
print_r($_SESSION['user_id']);
echo '</pre>';

if(isset($_SESSION['user_id'])){
	
	$user_id = $_SESSION['user_id'];
	$data = $user->userInfo($user_id);
	
	echo '<pre>';
	print_r($data);
	echo '</pre>';
	echo $data['username'],'<br />';

}else {
	echo 'bla';
}