Laravel 5.4 : creates database and runs Artisan::call('migrate') on it

It's been 2 days I'm trying to write a simple wizard installation for my due project, and I'm currently going nuts about a problem I can't solve.

The need
I'm developping a sorta wizard. This wizard asks for the usual DB settings : host, port, username, password, and database name.
I'm asked to create a database whose name comes from the form, and populate it with migrations and seeds defined in usual files.
I can't use the RachidLaasri github project, because specs cannot accept it.

What works
So far, I managed to create a database, using a low level connection (using new \mysqli). This step was necessary this way because we need to test every step of connection to return an appropriate error message.
Then, I rewrite the .env with parameters proven corrects, including database name. So far so good.

the problem
Except that when I run Artisan::call('migrate'), it runs on previous database name (the one in the .env before rewriting it). I tried everything I found, but can't figure out a solution.
So, now a bit of my code, simplifed for readability :

 // Try connection with provided settings
        $dbHost = $request->get('db_host');
        $dbPort = $request->get('db_port');
        $dbName = $request->get('db_name');
        $dbUsername = $request->get('db_username');
        $dbPassword = $request->get('db_password');

        try {
            $dbConnection = new \mysqli($dbHost,
                $dbUsername,
                $dbPassword,
                '',
                $dbPort
            );
        } catch (\Exception $e) {
            return redirect()->back()
                ->withInput($request->all())
                ->withErrors(['general' => trans('wizard.errors.dbInit') . $e->getMessage()]);
        }

        // Create database
        $sql = 'CREATE DATABASE ' . $dbName .
            ' CHARACTER SET utf8 COLLATE utf8_bin';
        $queryResult = $dbConnection->query($sql);
        // [...] Handling errors
        $dbConnection->close();

        // Writing .env file
        // [...] Checking and replacing params, writing file, catching errors

        // Executing artisan commands to create tables, and populate them with mandatory data
        Artisan::call("config:clear");

        // Setting the config to use the newly created database
        Config::set('database.connections.mysql.database', $dbName);
        // DB::select('USE ' . $dbName); // Throws : General error: 1 near "USE": syntax error (SQL: USE dbname)

        Artisan::call('migrate');
        Artisan::call('db:seed');
        dd('STAHP'); // TODO debug
        return redirect()->route('wizard.step2');

Migrations and seeds are always done on the previous DB_DATABASE value coming from .env file.
I'm out of solution, I don't know what to try.
thank you for your help.

via Chebli Mohamed