FWIW I have been using Apache and PHP from pkgsrc for ten years under
NetBSD and it works fine.
> [Sun Apr 26 08:26:18.591549 2015] [:crit] [pid 5005:tid
> 140187728347136] Apache is running a threaded MPM, but your PHP
> Module is not compiled to be threadsafe. You need to recompile PHP.
> AH00013: Pre-configuration failed
Maybe you need this in your mk.conf:
PKG_OPTIONS.php = maintainer-zts
PKG_OPTIONS.ap24-php55 = maintainer-zts