How to load libraries?

Now, I'm developing a web service to synchronize chats with the web and PocketMine-MP.
The web server uses Node.js. And using Socket.IO for chat synchronization.
I found this library when I was looking for a library that can use Socket.IO in PHP.
So I used the composer to install the library.
In order to load the library from the PocketMine-MP plugin after installing the library, I wrote the following code.

PHP:

<?php
namespace EasyCHAT;

require_once __DIR__ . '/vendor/autoload.php';
use PHPSocketIO\SocketIO;
use Workerman\Worker;

use pocketmine\Player;
use pocketmine\plugin\PluginBase;
use pocketmine\Server;
use pocketmine\event\Listener;
use pocketmine\event\player\PlayerChatEvent;
use pocketmine\utils\Config;

class EasyCHAT extends PluginBase implements Listener{
public $client;

public function onEnable(){
global $client;
    require_once __DIR__ . '/vendor/autoload.php';
    if(!file_exists($this->getDataFolder())){
    mkdir($this->getDataFolder(), 0744, true);
    $this->config = new Config($this->getDataFolder()."Data.json", Config::JSON);
    $this->config->set("ID", "");
    $this->config->save();
    }
    $this->config = new Config($this->getDataFolder()."Data.json", Config::JSON);
    $this->getServer()->getPluginManager()->registerEvents($this, $this);
    $io = new SocketIO('http://192.168.1.10:3000');
    $io->emit('roomin', '123456');
}

public function onChat(PlayerChatEvent $event){
    global $io;
    $Message = $event->getMessage();
    $PlayerName = $event->getPlayer()->getName();
    $array['id'] = $this->config->get('ID');
    $array['message'] = 'TESTMESSAGE';
    $io->emit('send', json_encode($array));
    Worker::runAll();
}
}

I tried starting up the server. But,

This error was output to the console.
The location of files is as follows.

Easy-CHAT.php
src|
-These files
vendor|
Files placed by composer

How to disappear errors and WebSocket communication will be possible?
Give me advices.

 

I used Miner to install.

 

Then, what should I do?

 

Are there other Socket.IO libraries that can be used with PMMP?
However, there are cases where Node.js sends messages to PMMP.

 

You have to register the namespace with PocketMine's auto Loader for it work.

 

What file namespace?
I found such a sentence in Miner's thread.

Could you tell me how to register with PocketMine's Autoloader?
Sorry to bother you again...

 

I examined it, but I could not understand it with my knowledge.
The sites I watched

http://qiita.com/inouet/items/0208237629496070bbd4
http://qiita.com/misogi@github/items/8d02f2eac9a91b4e6215
http://php-archive.net/php/class-autoload/

Would you please tell me where and how to change