You could also look for a slackware package for php-exif or such. I don't know how slackware does things, but debian has packages for all the addons.

What is the most effective way to get linux programs to compile (c++ or c files, using make or gmake) on OpenBSD ? I am having lots of troubles with people who have written c apps without other ...

Linux has come a long way from its roots, where users had to compile the kernel and all of the other source code from scratch, often without any internet connection at all to help with documentation.