PHP has its purpose which is developing simple sites fast. Python and Scala can do that too but they are much more sophisticated. Scala might one day compete with Java in the enterprise world. Hybrid languages on JVM are very interesting. On the front-end side, all can be done with JavaScript much nicer while having HTML completely separate. If you have a nice event-driven or service-oriented backend which responds to your Ajax calls, what the hell would you need the PHP for? The world is changing, I personally prefer to adapt to the change and not get used to mediocracy of hacking code fast.

I have recently started working on a service oriented single page webapp, I don't have much to back me up but I prefer to use Java with any of the available frameworks as my service layer and with a front-end which is built solely using HTML5, CSS3 and JavaScript. You can brag about Ajax security concerns, SEO and cross-browser compatibility all you want, but nothing will change the future. At least it is my belief about which direction web is moving towards.