[MyNameIsCode]

Это вот отсюда

function loginAction() {
    $username = isset($_REQUEST['username']) ? $_REQUEST['username'] : null;
    $username = trim($username);

    $password = isset($_REQUEST['password']) ? $_REQUEST['password'] : null;
    $password = trim($password);

    $userData = loginUser($username, $password);

    if($userData['success']) {
        $userData = $userData[0];

        $_SESSION['user'] = $userData;
        $_SESSION['user']['displayName'] = $userData['username'];

        $resData = $_SESSION['user'];
        $resData['success'] = 1;

    } else {
        $resData['success'] = 0;
        $resData['message'] = 'Неверный логин или пароль';
    }

    echo json_encode($resData);
}