Salary is not the only criterion - what if I mostly care about getting things done, not about becoming employed? (Not that I would choose PHP anyway, but still).
I am also not convinced that PHP just got lucky with the timing and that therefore there are no language design lessons to be learned. Perhaps if you get a noob into programming, they would still have an easier time with PHP than with more modern MVC based frameworks, because it is more straightforward. You still just write SQL directly in the code - it is messy, but easier to grasp than having to work through all sorts of layers of abstraction.
Maybe there IS a language lesson there - although I sure hope PHP is not the final answer...
Perhaps not a "language lesson", but PHP has a great deployment story: upload then refresh your browser.
PHP allows a strong separation between system administrator (who is running Apache) and the "application developers" who are people using FTP to upload their script files to a shared host. The simplicity of the system makes it easy for anyone to get started, hence the popularity.
There is also the bit about taking an existing UI (written in HTML) and being able to insert programming hooks into it at will. The "minimal change" is very small, the biggest step is changing the file extension from html to php.
I am also not convinced that PHP just got lucky with the timing and that therefore there are no language design lessons to be learned. Perhaps if you get a noob into programming, they would still have an easier time with PHP than with more modern MVC based frameworks, because it is more straightforward. You still just write SQL directly in the code - it is messy, but easier to grasp than having to work through all sorts of layers of abstraction.
Maybe there IS a language lesson there - although I sure hope PHP is not the final answer...