I am guessing that market share is defined such that each domain backed by a wordpress instance (wordpress being written in php) is counted as one share, and gm

I am guessing that market share is defined such that each domain backed by a wordpress instance (wordpress being written in php) is counted as one share, and gmail.com is counted as one share (or worse, because the survey cannot programmmatically determine what language gmail.com is written in, it is not represented at all in the count). I doubt more than 25% of the hours spent by programmers on software that runs on web servers is spent on PHP code.