Question: Is it possible to compile a program on linux using a .dll file?

Where this is going: This .dll will be used to write a php extension to some proprietary software from a third party.

Background and Research:

I have been given a library called proprietary.lib. I was curious, as I have never seen the .lib extension before, so I typed:

file proprietary.lib

The output was:

proprietary.lib:  current ar archive

I did some research and found that ar is more-or-less tar (and in fact, I guess tar has since replaced ar in most *nix environments).

Upon inspecting the ar manpage, I saw the t option, which displays a table listing of the contents of that archive. Cool. So I type:

ar t proprietary.lib

And get:

proprietary.dll
proprietary.dll
... (snip X lines) ...