On the SitePoint PHP blog there's a tutorial posted helping you get started editing and updating the PHP.net documentation, one of the most widely used parts of the PHP ecosystem.
In this two-part article series, we’ll be covering how to contribute to the PHP project. This will hopefully clarify what steps need to be taken for those looking to become more involved with PHP.
This first part will be covering how to contribute to PHP’s documentation, including how to request a php.net Account and what to do once an account has been granted.
He starts with a bit about why you should contribute back to the PHP project and how the documentation is a great place to start. He then gets into the structure of the documentation, the DocBook structure it uses and points to the online editor for the first time contributors. He includes a video showing how to use the system to resolve this bug showing an incorrect MongoDB
Client example. For those that would rather do it locally, he shows how to setup and configure the source and required tools. He then shows the flow of updating the documentation, building the result and verifying the update looks correct.
Finally he talks about requesting a php.net account to push the changes back upstream and provides some general tips on things like style guidelines, page ordering and correctly versioning files.