Building own/not existing php module (rdkafka)


I’m trying to add a php module which relies on rdkafka library for a nix shell dev environment.
I followed the way with the peclBuild method according to the nix pkgs repository. Unfortunately I run into thefollowing error during the phpize command:

checking for rdkafka support... yes, shared
checking for librdkafka/rdkafka.h" in default path... not found

Is there any option that I can activate to make the header files available?
I am pretty new to Nix and NixOS. So I am thankful for any hints or advises.

Thanks a lot in advance