Laravel get query string

As far as Laravel 5.7 is concerned, the preferred way to retrieve query params is

if( $request->has('invitee') ) {
    $request->query('invitee');
}

or using the helper function if you don't have access to $request

request()->query('invitee');

In laravel 5.7, we can also use request()->invitee. By using this, we can get both, URL path parameters and query parameters. Say we have below URL

http://localhost:8000/users/{id}?invitee=95

To read id and invitee, we can use

$id  ✔
$invitee ✖ - Invalid
request()->id ✔
request()->invitee ✔

You can get input by:

$invitee = Input::get('invitee');

For above 5.*

$invitee = $request->input('invitee');

Or

$invitee = Request::input('invitee');

To check if invitee parameter exists:

if($request->has('invitee')) {
    // ...
}

To get the value of invitee:

$invitee = $request->input('invitee');

Are you calling $user->save() anywhere? You should call $user->save() to actually persist the data.

You can always check by calling dd($user); right after the second line in you example if you are worried it is not set correctly, this way you can see what attributes are set in the $user object.

Also you can replace !empty($request->get('invitee')) with $request->has('invitee').

Since so many different answers have accumulated here, let me clear up the confusion.

->has(), ->query(), ->input(),...

What do we need to check for a query param and get its value?

The clean minimal solution

$value = $request->query('name');
if ($value) {
    // work with the value
}

As stated in Laravel's official documentation section Retrieving Input From the Query String the $request->query('name') is specifically designed to "retrieve values from the query string".

If the method returns null, the param wasn't passed at all or without a value. So with the if condition, we ensure an actual $value.

The all-rounder solution

$request->input() is similar to $request->query(), but it's more general. It does not only work for checking query strings, but also for form data sent via POST, JSON payloads, XHR requests,...

$request->has() checks the sources that the ->input() method draws from.

So this solution works great, too:

if($request->has('name')) {
    $value = $request->input('name');
    // work with the value
}

It works not only for GET requests with query params, but a lot more.

Regarding the OP's code

You're officially discouraged to use the $request->get() method:

This method belongs to Symfony HttpFoundation and is not usually needed when using Laravel.
Instead, you may use the "input" method.