Atlassian Confluence Server for Windows is bundled with a web server which runs on port 8090. Most organisations would rather a more user-friendly URL such as confluence.domain.com. Although this isn't technically supported by Atlassian, it's best practice to leave this port as is and instead implement a Reverse Proxy.
Installing PHP on IIS is fairly straight forward using Microsoft’s Web Platform Installer. Unfortuantely numerous resources available on the web as well as the Web Platform Installer’s prerequisite check overlook a few prerequisites when installing PHP on IIS running on Windows Server. I’ve developed a guide and a list of requirements that will make the process of installing PHP on IIS much easier.