How to download workerman

<?php
use Workerman\Worker;
 
//Autoloader.php路径
require_once "./Autoloader.php";
 
$global_uid = 0;
 
// 当客户端连上来时分配uid，并保存连接，并通知所有客户端
function handle_connection($connection)
{
    global $text_worker, $global_uid;
    // 为这个连接分配一个uid
    $connection->uid = ++$global_uid;
}
 
// 当客户端发送消息过来时，转发给所有人
function handle_message($connection, $data)
{
    global $text_worker;
    foreach($text_worker->connections as $conn)
    {
        $conn->send("user[{$connection->uid}] said: $data");
    }
}
 
// 当客户端断开时，广播给所有客户端
function handle_close($connection)
{
    global $text_worker;
    foreach($text_worker->connections as $conn)
    {
        $conn->send("user[{$connection->uid}] logout");
    }
}
 
// 创建一个文本协议的Worker监听2000接口  用0.0.0.0方便链接内网外网
$text_worker = new Worker("websocket://0.0.0.0:2000");  
 
// 只启动1个进程，这样方便客户端之间传输数据
$text_worker->count = 1;
 
$text_worker->onConnect = &#39;handle_connection&#39;;
$text_worker->onMessage = &#39;handle_message&#39;;
$text_worker->onClose = &#39;handle_close&#39;;
 
Worker::runAll();

// 假设服务端ip为127.0.0.1
ws = new WebSocket("ws://127.0.0.1:2000");
ws.onopen = function() {
    alert("连接成功");
    ws.send('我是谁？');
    alert("给服务端发送一个字符串：我是谁？");
};
ws.onmessage = function(e) {
    alert("收到服务端的消息：" + e.data);
};