A recent small project at work called for using WordPress as a Basic LTI Tool Consumer. Basic LTI is a dirt-simple, and quite handy, way to integrate web applications and is especially popular in the education industry.
We ended up creating a simple WordPress plugin. The plugin has some proprietary bits, but I've extracted the core logic into a gist for your enjoyment. Hopefully this is helpful for you PHP hackers out there, or anyone else needing a simple example of how Basic LTI works.