Would it be bad to just drop the --with-mysql, since it is deprecated and mysqli has been available since 5.0?

Other than my question, LGTM.

I thought about that, I think leaving it in is probably the right call since people might want to migrate old codebases into docker. I don't do much php development though (only noticed this when migrating some hackerspace projects into docker), so maybe someone with more PHP experience can chime in?

I'm +1 on keeping both, especially since the older stuff is still in pretty
wide use.

Then what about PDO?

That's a good point, I didn't add PDO as I wasn't that familiar with it. I'm usually averse to adding a million compile flags, but it probably makes sense as this is supposed to be a base language pack.

I'll add it to this PR if you two think it's the right way to go.

Sounds good to me. @tianon?