[php-src] Issue #8239: For php://input fread() writes temp files

Issue: https://github.com/php/php-src/issues/8239 Comment Author: cmb69 To be able to apply stream operations, there needs to be a stream. Always forcing a memory stream could deploy the available memory on the system, but maybe we should think about increasing the threshold; the current 0x4000 might be anachronistic. And yes, we also could introduce an INI setting for this. The current behavior doesn't look like a bug to me, though, so I'm changing to feature request. And while I don't think this needs an RFC, at least some discussion on the [internals mailing list](https://www.php.net/mailing-lists.php#internals) appears to be in order.