Laravel uploaded file name change is not working

So I'm uploading an image and I want to change the name of it to:

logo_{{Auth::user()->firstName}}_{{Auth::user()->lastName}} 

and I want to keep the extension. In my controller I have :

<?php namespace App\Http\Controllers;

use Illuminate\Support\Facades\Input;

class UploadController extends Controller {

    public function upload(){

        if(Input::hasFile('file')){

            echo 'Uploaded';

            $file = Input::file('file');
            $file->move('uploads  ', $file->getClientOriginalName());
            $custom_name = 'logo_{{Auth::user()->firstName}}_{{Auth::user()->lastName}}'.$file->getClientOriginalExtension();
            echo '<img src="uploads/' . $file->getClientOriginalName() . '"/>';
        }

    }
}

So yes actually it's getClientOriginalName so ofc it will keep the same name, but how can I change it like this?