PHP programing language is specialized for web application development. That's a rare language. But, even if there is a all-purpose programing language, that is not a reason why you choose the language. Because, most programers are not almighty.
Let's think that your company develops a new blu-ray recorder. And, it's possible to develop both of web page and firmware by using Java. Can Java programers begin firmware development after web page development? An answer is "No".
Programers bring to experience(knowhow) not programming language. Embedded programmers have rich experience to control hardware. Web programmers have rich experience to realize web service. It's easy that web application developers master other programming language for web application development. However, it's difficult that web application developers master embedded software for hardware, even if it's possible to write embedded program in the same programing language that they always use.
All-purpose programing language for many categories is very good. But, that's nonsense for most programers. That's the actual skill of most programers. Meanwhile your experience on web application development is useful for any programing languages. It's important what you've experienced, not what programing language you can use.
What's interesting is that programming languages don't have difference on web application spec. So, to take advantage of your experiences, we should choose the best environment suited to the times.