That eighty percent number is fun
Eighty percent of PHP applications are built on Windows but are not deployed on Windows, which means lost business and lost developers who'd otherwise help maintain and perpetuate the platform.
Well well, I don't know... server stability perhaps?
Integration of PHP into *lame* IIS?
*lame* IIS itself?
Or might it be that PHP is a rather "cheap" language, that doesn't require very extensive skills (don't flame, I dev in php) ?
Cheap language, free server, happy small businesses...
Who's ever gonna buy a W2K3 license just to host an internal application or whatever