fopen and stream_select not working after PHP 8 upgrade

I upgraded a PHP 7 application to PHP 8. The following code was working before, but no longer:

$options = [
    'http' => [
        'method' => 'POST',
        'header' => "Content-Type: application/x-www-form-urlencoded\r\n"
            . 'Content-Length: ' . strlen($content),
        'content' => $content,
        'timeout' => 30,
    ],
];
$context = stream_context_create($options);
$stream = fopen($url, 'r', false, $context);

$read[] = $stream;
$write = null;
$except = null;
$streamsChanged = stream_select($read, $write, $except, 0, 50000);

Now the call to stream_select produces the following error:

Type: ValueError
Message: No stream arrays were passed

I've tried the same POST call using Insomnia without any issues, so it does appear to be related to how I'm using PHP 8.

A var_dump of $stream returns resource(stream), so the type seems correct. I also ran:

is_resource($stream) 
    && get_resource_type($stream) === 'stream' 
    && !feof($stream)

and it passed.

Solution

It is a known issue in PHP 8.x

In PHP 8.0+, the default protocol_version for an HTTP context changed to 1.1. HTTP/1.1 often uses Transfer-Encoding: chunked, which PHP implements internally as a filter, triggering this error when stream_select() is used.

One of the solutions is forcing the use of HTTP/1.0 in order to avoid the implicit chunked encoding filter.

For PHP , it is like:

  'http' => [
        'protocol_version' => '1.0',
  // other parameters...
    ]

So, the following code will be fine:

<?php

$url="https://somedomain.com/index.php";

$content='test_data';

$options = [
    'http' => [
        'protocol_version' => '1.0',
        'method' => 'POST',
        'header' => "Content-Type: application/x-www-form-urlencoded\r\n"
            . 'Content-Length: ' . strlen($content),
        'content' => $content,
        'timeout' => 30,
    ],
];
$context = stream_context_create($options);
$stream = fopen($url, 'r', false, $context);

if (is_resource($stream) && get_resource_type($stream) === 'stream' && !feof($stream)) { 
   // echo "ok";
}

$read[] = $stream;
$write = null;
$except = null;
$streamsChanged = stream_select($read, $write, $except, 0, 50000);

// echo $streamsChanged; (it may now return say 1)
?>

Apart from the above simple method, the following are other alternatives :

Avoid using stream_select() on filtered streams (and so you have to amend your code to use other commands to achieve what you want)
Use non-blocking streams: Ensure all streams passed to stream_select() are explicitly set to non-blocking mode
Try using a robust library: Consider using an external library that contains internal workarounds to tackle this issue (in my understanding ReactPHP's Event Loop is one of the possible libraries)