ChatController.php

// [...]

    /**
     * Create or get channel
     */
    public function createOrGetChannel(Request $request)
    {
        $from = $request->input('from');
        $to = $request->input('to');

        $from_username = $request->input('from_username');
        $to_username = $request->input('to_username');

        $channel = Channel::whereIn('from_id', [$from, $to])
                           ->whereIn('to_id', [$from, $to])
                           ->first();

        // If channel if already created,return it else create it.
        if ($channel) { 
            $channel_name = $channel->name;
        } else {
            $channel_name = "private-{$from_username}-{$to_username}";
            
            $channel = new Channel();
            $channel->name = $channel_name;
            $channel->from_id = $from;
            $channel->to_id = $to;
            $channel->save();

            // Create channel to Stream Chat
            $channel = $this->client->getChannel("messaging", $channel_name);
            $channel->create($from_username, [$to_username]);
        }
        
        return response()->json([
            'channel' => $channel_name
        ], 200);
    }

// [...]