Private channel not working with Laravel echo server

I'm getting this JS error on the console:

app.js:167 Uncaught ReferenceError: receiverId is not defined

Here is my complete code:

PrivateChatController:

event(new PrivateMessageEvent($chat, $receiverId));

PrivateMessageEvent:

namespace App\Events;

use Illuminate\Broadcasting\Channel;
use Illuminate\Queue\SerializesModels;
use Illuminate\Broadcasting\PrivateChannel;
use Illuminate\Broadcasting\PresenceChannel;
use Illuminate\Foundation\Events\Dispatchable;
use Illuminate\Broadcasting\InteractsWithSockets;
use Illuminate\Contracts\Broadcasting\ShouldBroadcast;
use App\User;
use App\PrivateChat;

class PrivateMessageEvent implements ShouldBroadcast
{
    use Dispatchable, InteractsWithSockets, SerializesModels;

    public $privateChat, $receiverId;
    /**
     * Create a new event instance.
     *
     * @return void
     */
    public function __construct(PrivateChat $privateChat, $receiverId)
    {
        $this->privateChat = $privateChat;
        $this->$receiverId = $receiverId;
    }

    /**
     * Get the channels the event should broadcast on.
     *
     * @return Channel|array
     */
    public function broadcastOn()
    {
        return new PrivateChannel('private-chat.' . $this->receiverId);
    }
}

Bootstrap.js

import Echo from "laravel-echo"

window.Echo = new Echo({
    broadcaster: 'socket.io',
    host: window.location.hostname + ':6001'
});

window.Echo.private(`private-chat.${receiverId}`)
    .listen('PrivateMessageEvent', (e) => {
        console.log(e);
});

channels.php

Broadcast::channel('private-chat.{receiverId}', function ($user, $receiverId) {
    return true; // this is just for debugging to allow anyone to listen on this channel
    //return $user->id === $receiverId;
});

laravel-echo-server.json

{
    "authHost": "http://localhost",
    "authEndpoint": "/broadcasting/auth",
    "clients": [],
    "database": "redis",
    "databaseConfig": {
        "redis": {},
        "sqlite": {
            "databasePath": "/database/laravel-echo-server.sqlite"
        }
    },
    "devMode": true,
    "host": null,
    "port": "6001",
    "protocol": "http",
    "socketio": {},
    "sslCertPath": "",
    "sslKeyPath": ""
}

In background queue:work and laravel-echo-server are already running

Upon firing that event, I'm getting this message on the laravel-echo-server console:

Channel: private-private-chat.
Event: App\Events\PrivateMessageEvent
CHANNEL private-private-chat.

Notes:

• I'm successfully able to listen to the public channel. The only issue with the private channel.

• Using latest Laravel version i.e 5.4

• I have done all the things as per the official docs:

  https://laravel.com/docs/master/broadcasting

  https://github.com/tlaverdure/laravel-echo-server

• I have also raised issue on github repo:

  https://github.com/tlaverdure/laravel-echo-server/issues/158

I have spent more than 10 hours and tried everything I could, but no luck.

Thanks

via Parth Vora