How to access session data in OpenSwoole WebSocket server?

Question

I have a small websocket server implemented in OpenSwoole. Is there a way to access the users session data? I tried this:

<?php

use Swoole\WebSocket\Server;
use Swoole\Http\Request;
use Swoole\WebSocket\Frame;

$server = new Server("0.0.0.0", 9502);

$server->on("Start", function(Server $server)
{
    echo "Swoole WebSocket Server is started at http://127.0.0.1:9502\n";
});

$server->on('Open', function(Server $server, Swoole\Http\Request $request)
{
    echo "connection open: {$request->fd}\n";
    var_dump($request->cookie);
    echo "using session id ".$request->cookie['PHPSESSID']."\n";
    session_id(trim($request->cookie['PHPSESSID']));
    session_start();
    echo "user: ".$_SESSION['id_user'];
});
$server->on('Message', function(Server $server, Frame $frame)
{
    echo "received message: {$frame->data}\n";
   
    $server->push($frame->fd, json_encode(["hello", time()]));
});

$server->on('Close', function(Server $server, int $fd)
{
    echo "connection close: {$fd}\n";
});

$server->on('Disconnect', function(Server $server, int $fd)
{
    echo "connection disconnect: {$fd}\n";
});

which gives me this when a client connects:

# php websocket.php 
Swoole WebSocket Server is started at http://127.0.0.1:9502
connection open: 1
array(1) {
  ["PHPSESSID"]=>
  string(26) "humr1mg4s26jp5fqkavih6tutf"
}
using session id humr1mg4s26jp5fqkavih6tutf
PHP Warning:  session_id(): Session ID cannot be changed after headers have already been sent in websocket.php on line 19
PHP Warning:  session_start(): Session cannot be started after headers have already been sent in websocket.php on line 20
PHP Warning:  Undefined variable $_SESSION in websocket.php on line 21
PHP Warning:  Trying to access array offset on value of type null in websocket.php on line 21
user:

Is there a way to start the users PHP session from the websocket server? The users session itself is started by the website's PHP code hosted on Apache.

Answer 1

Looks like the echo calls on the websocket server trigger the "header already send" errors. Using this works:

$server->on('Open', function(Server $server, Swoole\Http\Request $request)
{
    session_id(trim($request->cookie['PHPSESSID']));
    session_start();
    // Do something ... and close the session afterwards.
    session_write_close();
});

Second, the websocket server has to be started using apache's system user for having access to the session data:

# sudo -u www-data php websocket.php