Many mqtt ClientBuilder in Php

I would like to have several ClientBuilders in php and have them all run at the same time. At the moment I can create one but when I add a new one, the part :

$mqtt->loop(true)

blocks the execution of the new ClientBuilder.

At the moment I use the ClientBuilder and I proceed in the following way:

$connectionSettings = (new \PhpMqtt\Client\ConnectionSettings)
     ->setUsername("username")
     ->setPassword("passwd")
     ->setConnectTimeout(3)
     ->setUseTls(false);
$connectionSettings2 = (new \PhpMqtt\Client\ConnectionSettings)
     ->setUsername("username2")
     ->setPassword("passw2")
     ->setConnectTimeout(3)
     ->setUseTls(false);
$mqtt = ClientBuilder::create();
$mqtt2 = ClientBuilder::create();

try {
   $mqtt->connect($connectionSettings, true);
   $mqtt2->connect($connectionSettings2, true);
} catch (\Exception $e) {
   $io->error(__('Error to connect {0}', $e->getMessage()));
}
$filter = 'filter01';
$filter2 = 'filter02';
$idStartAt = strlen($filter) - 1;
$idStartAt2 = strlen($filter2) - 1;
$mqtt->subscribe($filter, function ($topic, $message) use ($idStartAt, $io) {
   $this->fct($topic, $idStartAt, $message, $io);
}, 0);
$mqtt2->subscribe($filter2, function ($topic, $message) use ($idStartAt2, $io) {
   $this->fct2($topic, $idStartAt2, $message, $io);
}, 0);

$mqtt->loop(true);
$mqtt2->loop(true);

$mqtt->disconnect();
$mqtt2->disconnect();

What can I do?

As you have discovered, loop(true) blocks forever and code after $mqtt->loop(true) will not run until the loop exits. The loop() method (with your parameters) is effectively:

$loopStartedAt = microtime(true);
while (true) {
    $this->loopOnce($loopStartedAt, true);
}

The docs for loopOnce() say:

> Runs an event loop iteration that handles messages from the server and calls the registered callbacks for published messages. Also resends pending messages and calls loop event handlers. This method can be used to integrate the MQTT client in another event loop (like ReactPHP or Ratchet).
> Note: To ensure the event handlers called by this method will receive the correct elapsed time, the caller is responsible to provide the correct starting time of the loop as returned by microtime(true).

So you should be able to replace

$mqtt->loop(true);
$mqtt2->loop(true);

with something like:

$loopStartedAt = microtime(true);
while (true) {
    $mqtt->loopOnce($loopStartedAt, false);
    $mqtt2->loopOnce($loopStartedAt, false);
    usleep(100000);
}

You probably want to add an exit condition (see the source for loop() for an example of how this might work).

Note: I have not tested this code.
Note2: Multiple connections to the same broker might not be the best solution (but you have not described your aim so it's difficulty to comment further).