The optional parameter in the route does not work

Question

I'm having a problem with the optional parameter; in particular I notice that it is not read in the link.

I explain in detail: in the view I have a table with several clients. In this table there is a column with the active projects for each customer (through the CLient_id foreign key present in the Projects table).

So what I want is that when I click on that client's number of active projects, it shows me these active projects.

ROUTE:

Route::get('/project/index/{id?}', [ProjectController::class, 'index'])->name('project.index');

ProjectController:

public function index($id = NULL)
    {   
        if($id){
            $projects = Project::where('client_id', $id)->get();
        } else {
            $projects = Project::all();
        }
        return view('project.index', compact('projects'));
    }

View:

<tr>
                <th>ID</th>
                <th>Name</th>
                <th>Email</th>
                <th>Address</th>
                <th>N. active projects</th>
            </tr>
            @foreach ($clients as $client)
            <tr>
                <td>{{ $client->id }}</td>
                <td>{{ $client->name }}</td>
                <td>{{ $client->email }}</td>
                <td>{{ $client->address }}</td>
                <td><a href="{{route('project.index')}}" class="link-primary">{{ $client->projects_count }}</a></td>
                <td>    

When I click on the number of active projects of that client, it always takes me back to the index where ALL the projects are present.

Answer 1

The parameter is working as expected. Change

<td><a href="{{route('project.index')}}" class="link-primary">{{ $client->projects_count }}</a></td>

to

<td><a href="{{route('project.index', ['id' => $client->id])}}" class="link-primary">{{ $client->projects_count }}</a></td>

to actually pass the $id to the controller.