Add missing ext/libxml dependency to ext/xmlwriter

[petk]

This adds the libxml extension to required dependencies for xmlwriter during the configuration phase (PHP_ADD_EXTENSION_DEP) and the runtime (ZEND_MOD_REQUIRED).

I'm not sure if there is some internal limitation on adding these ZEND_MOD_* dependencies. Would this cause any performance overhead? These are also used so that extensions are sorted properly when being registered into the Zend hash table.

[nielsdos]

Interesting...
Technically, ext-libxml isn't required for this extension to work in a "minimal way"; but it is necessary to make it work properly (i.e. have proper error reporting etc).

The same problem may exist for ext-xmlreader.

I'm not sure if there is some internal limitation on adding these ZEND_MOD_* dependencies. Would this cause any performance overhead? These are also used so that extensions are sorted properly when being registered into the Zend hash table.

Doubt this will cause much overhead at all; it's only checked on startup anyway.

[petk]

I see, thanks for the info. The xmlwriter works without libxml extension but in a limited way. 🤔 I'll add this info in the commit message.

[nielsdos]

The xmlwriter works without libxml extension but in a limited way.

I'll clarify a bit. It's an extension that uses libxml to do its work. We have a support layer in PHP for all extensions that use libxml, it's the "libxml" extension, i.e. the code in ext/libxml. While some extension (like xmlwriter) can work without that support layer, it would not be able to use proper error reporting or have support for streams without it.

[petk]

I've merged it now in the master branch. I hope I wasn't too quick. We can refactor this in the near future if needed.

[nielsdos]

I've merged it now in the master branch. I hope I wasn't too quick. We can refactor this in the near future if needed.

No, your PR is fine.