For php://input fread() writes temp files

Description

The following code:

<?php
// index.php

$postBodyResource = fopen("php://input", 'rb');
while (!feof($postBodyResource)) {
    $data = fread($postBodyResource, 5 * 1024);
}
fclose($postBodyResource);

and Apache 2.4 config

Alias "/api" "${SRVROOT}/htdocs/Api"
<Directory "${SRVROOT}/htdocs/Api">
    RewriteEngine On 
    RewriteCond %{REQUEST_FILEaNAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^ index.php [QSA,L]

    Script POST "index.php"
    Script PUT "index.php"

    php_value enable_post_data_reading Off
</Directory>

Resulted in this output:
If I do a HTTP POST (Content-Type: application/octet-stream) at http://localhost/api with a body larger than 16 kB, PHP creates a temp file at sys_temp_dir or upload_dir that stores the whole content of the stream php://input while doing fread().

But I expected this output instead:
At least there should be a configuration option to disable writing the temp files.

See temp file writing so caused by php_fopen_wrapper.c#L231.

Please, see Stackoverflow for some discussion.

PHP Version

PHP 7.4+

Operating System

Windows 10 21H2

Start with ext/standard/php_fopen_wrapper.c at the linked line and reproduce the PHP 7.4+ behavior using the provided script, Apache configuration, and a POST body over 16 kB on Windows. Trace why php://input writes the complete stream to a temporary file; done means the reported behavior or its configuration control is addressed and covered by a regression test.