From my memory (which is not the most reliable source) it was a co-dependent relationship initially. PHP gained acceptance as a language for open source web pro

From my memory (which is not the most reliable source) it was a co-dependent relationship initially. PHP gained acceptance as a language for open source web projects, which lead to the likes of phpBB and Wordpress which in turn lead to PHP gaining even more presence on the web. I think the staying power of php is at least in part due to the continued success of popular projects that rely on it, whoever was responsible for its initial successes.