I have no problem with PHP in general; I don't like the tooling as much as I like what is available for .NET. It as always come down to the reputation that PHP has gained as being "insecure". This is mostly reputation (although not entirely un-earned) and not core fact though.
The biggest thing is PHP is very easy to write poorly. Given that WP is based on it and the issues with WP security mostly boils down to poorly written plugins; it isn't impossible to see how we got here and why we are still here. Any code in any language when written poorly, is bad; and that is hardly the languages "fault".
The latest iterations of PHP have impressed me; but it still won't be my go-to solution based on my experience with other languages being greater and wider-reaching.
I do think getting statistics on usage is going to be difficult at best and wildly inaccurate at worst. There are so many "web based" solutions that you'll never see on the internet. PHP most likely makes up far less of the world than these surveys imply.