RegisterController.php

// app/Http/Controllers/Auth/RegisterController.php

// first import StreamChat PHP client
use GetStream\StreamChat\Client as StreamClient;

protected function registered($user){
    $client = new StreamClient(env("MIX_STREAM_API_KEY"), env("MIX_STREAM_API_SECRET"), null, null, 9);

    $username = explode('@', $user->email)[0];

    // create the user on Stream Chat
    $client->updateUser([
        'id' => $username,
        'name' => $user->name,
    ]);

    // create channel
    $channel = $client->Channel("messaging", "chatroom");

    // channel is created by `admin` user
    $channel->create('admin');

    // then add the newly registered user as a member
    $channel->addMembers([$username]);
}