Some questions about PHP Dev. from an open source perspective

Hi there, My name is Kin Lau and I'm doing some study on open source projects. I would like to take a look at PHP, but I'm having some difficulties finding the all the information the web. I'd be much obliged if anyone could provide any extra information on the questions/aspects for PHP below. Just whatever you know for any of them, don't have to answer all of them: Questions: -How do decision processes work in os projects? Is this also open to the whole community? -How is QA/testing done and why is it effective? (reputation in os is an important aspect) -How is reusability working and why is it so effective in open source? -What are the incentives for developers in os development? Aspects: -Structure of development team (hierarchy) -Distribution of development team -Type of developers -> Employed? Students? Other individuals? -Defect tracking -QA -Requirements -Documentation -Reviews -Transparency -Planning (versions, etc.. stable/unstable) -Communication style/tools -Change tracking -Tools (web sites, builds, change management, newsgroups, forums, etc..) -How successful is the feedback loop (contributions from outside core team/company contributions) Thank you very much for your time! Sincerely, - Kin