The Apache HTTP server, also an open-source software project and used in more Web sites than all other Web servers combined, delivers Web pages constructed by PHP to the Web. In this project, it simply operates behind the scenes with scarcely any requirement beyond initial configuration during installation.

Linux, similarly operating behind the scenes, provides the basis on which all the software works, apportioning computer resources among the programs such that all seem to work simultaneously. It is a UNIX-based system invented by Linus Torvalds while he was a graduate student and since developed by a large open-source community of contributors.