Can't pass an argument to pool function

[BanterFace]

Hi there. PHP 7.4.0RC1, CentOS 7.6.1810. Setup using composer.
Trying to execute this code:

<?php
require_once('/root/vendor/autoload.php');
use Spatie\Async\Pool;
$pool = Pool::create();

$collect = 'COLLECT';
for ($i=0; $i < 3; $i++) { 
	$pool -> add(function() use($collect){
		$collect .= "\n" . 1;
	}) -> catch(function($exception){
		echo($exception . "\n");
	});
}
$pool->wait();

echo($collect);

Got 3 warnings like that:

Spatie\Async\Output\ParallelError: PHP Warning: include(): Opis\Closure\ClosureStream::stream_set_option is not implemented! in /root/vendor/opis/closure/src/SerializableClosure.php on line 257
in /root/vendor/spatie/async/src/Output/ParallelError.php:11
Stack trace:
#0 /root/vendor/spatie/async/src/Process/ParallelProcess.php(126): Spatie\Async\Output\ParallelError::fromException()
#1 /root/vendor/spatie/async/src/Process/ProcessCallbacks.php(54): Spatie\Async\Process\ParallelProcess->resolveErrorOutput()
#2 /root/vendor/spatie/async/src/Process/ProcessCallbacks.php(38): Spatie\Async\Process\ParallelProcess->triggerError()
#3 /root/vendor/spatie/async/src/Pool.php(182): Spatie\Async\Process\ParallelProcess->triggerSuccess()
#4 /root/vendor/spatie/async/src/Pool.php(295): Spatie\Async\Pool->markAsFinished()
#5 /root/vendor/spatie/async/src/Pool.php(131): Spatie\Async\Pool->Spatie\Async{closure}()
#6 /home/tor-fake/web/hydraruma6mcunvp.onion/public_html/test.php(14): Spatie\Async\Pool->wait()
#7 {main}

...but, most importantly, the function does not work at all, at the end php echoes just 'COLLECT', while it should be different as you may see.
Can anyone please say what exactly I do wrong?

[brendt]

You would have to use a reference to $collect if you want to change it:

use(&$collect){

As to the error: it looks like your PHP installation is missing some stream-related functionality? If you want to get to the source of the problem, I recommend debugging in the opis package: https://github.com/opis/closure/blob/master/src/SerializableClosure.php