requirement to load libzstd.dll since PHP 8.5.7 when running as Apache module on Windows

[DanielRuf]

We have the following setup:

• PHP 8.5.7 with curl extension loaded
• Apache 2.4.68 from ApacheLounge
• PHP running as Apache module via LoadModule php_module "${basePath}/php/php8apache2_4.dll"

With PHP 8.5.2 curl (before curl 3.20.0) did not yet have a requirement to load libzstd. But now we have to add the following, to get it loaded according to phpinfo:

LoadFile "${basePath}/php/libzstd.dll"

Without this line it does not work.

So my questions are:

• should this extra LoadFile be documented, since without it setups will fail to load the curl extension?
• is there some mismatch between the ApacheLounge Apache builds and the newer PHP releases caused by some change in the curl extension?

ApacheLounge Apache 2.4.68 ships with zstd and brotli, so my assumption is that I should not have to add this extra LoadFile to my httpd.conf after LoadModule php_module "${basePath}/php/php8apache2_4.dll".

See https://www.apachelounge.com/viewtopic.php?p=44434 for reference and more context.

[shivammathur]

Rather than documenting this, I would like to solve this. Linking zstd statically in curl can be a solution on the PHP side.

@Jan-E What are your thoughts on this?

[Jan-E]

I am in strong favour of linking statically. In fact I link every dependency except OpenSSL statically in my own builds of php_curl.dll. Even nghttp2 and ssh2.

Problems like @DanielRuf is struggling with in https://www.apachelounge.com/viewtopic.php?p=44429#44429 (Thu 18 Jun '26 8:49) are typically the kind of problems you would expect when both Apache and PHP as Apache-module require a same dependency.

Would you also link brotli statically besides zstd? Then only PHP 8.5.7 and maybe 8.5.8 differ from previous 8.5.x builds with respect to dependent DLL's. And backport this change as far as possible. Even to PHP 8.2.x although a next release might take a long time (if ever).

[shivammathur]

@Jan-E

I would like to do a minimal change here for only zstd and keep brotli as it is since we don't have different file names for brotli DLLs and Apache ships them.

This should be a change only in the zstd and curl builds. No source change here in php-src and the extensions should be needed as they would pick the libcurl_a.lib with libzstd_a.lib statically linked in it.

Yes, next 8.2 and 8.3 releases should have the fixes as we build the dependencies for vs16.

[Jan-E]

Fine with me.

[Jan-E]

Any idea what caused the difference on (lib)zstd.dll names? Don't you use cmake like Apachelounge does? They are using https://github.com/facebook/zstd/tree/dev/build/cmake

[Jan-E]

I do not see a zstd project in winlibs. For my builds I downloaded a version from https://downloads.php.net/~windows/php-sdk/deps/
Both Apachelounge and PHP use the same zstd version.

[shivammathur]

We do not have a fork for zstd, it is directly pulled from facebook/zstd. it is because of this patch in winlib-builder that we have a different filename. I'm not sure why @cmb69 added it initially. Maybe he was following a convention we have to use the lib prefix.

[Jan-E]

Right. That convention seems to erode a little bit. See the changes in DLL-names in zlib 1.3.2. Which does not have an effect on PHP, because you are using zlib_a.lib statically afaik.

[shivammathur]

Yes, that is correct and it can be a good thing that we set a custom lib name in such cases, otherwise it would need changes across extensions that depend on zlib.

Fixed in winlibs/winlib-builder@1d73dee. Next releases should not require LoadFile "${basePath}/php/libzstd.dll".