Fix GH-8699: ini_get() opcache optimization in 8.1

[bix0r]

This fixes #8699 for PHP-8.1.
Can also be used for 8.0 and 7.4.

For 8.2, the problematic code has been moved to zend_optimizer.c.

[bukka]

I think it makes sense from the FPM PoV not to do this optimization because it can be changed using PHP_ADMIN_VALUE. @dstogov are you fine with this change?

[dstogov]

I'm not sure if this is a bug and if it should be fixed.

By design, ZEND_INI_SYSTEM setting are set once during PHP startup and cannot be changed. Settings that may be changed per-request should be ZEND_INI_PERDIR. FPM ignores this, but this doesn't mean overriding of all ZEND_INI_SYSTEM will work.

[bukka]

@dstogov You are right in principle. However PHP_ADMIN_VALUE is a bit special use case as it allows controlling ini settings from the server which is often used for the whole pool in the same way like defining the ini in the config. It actually works in a way that as soon as it is sent, then it impact all requests in the pool even if it is sent just once. Not sure if that's the right thing to do but that's how it currently works. Anyway it is still useful to allow changing any settings in this way. As you can see in the bug report, it's a perfectly valid use case and for many users this optimizations is not really worth loosing that functionality. Do you see actually some visible impact of this optimization? If so, maybe we could make the optimization optional?

[bukka]

That said I would agree that it's not exactly a bug and I'd rather not change in the patch release. This slightly protects people that expose FPM to public network as we had bunch of reports about allowing anyone to set PHP_ADMIN_VALUE. I know it is a terrible idea but people do that sometimes unknowingly and this might actually protect them a little bit. So we should at least introduce optional disabling of PHP_ADMIN_VALUE in FPM before removing this optimization.

[dstogov]

The proper solution would be adding ZEND_INI_PERDIR or some new (e.g.ZEND_INI_ADMIN) to ini settings that might be modified through PHP_ADMIN_VALUE.

[bukka]

Ok I think introducing new ZEND_INI_ADMIN is probably the way to go as it is a bit more special and we can careful pick all the supported options specifically for this use case.