One can do a lot of goods with PHP, Ruby and Python and any other languages/frameworks. It's not really the language but what you choose to do with it as well as your experience using it that will make your project. The only way to gain more experience is to start using it.
My feeling is, you want to pick something that will solve all your present problems and future proof. That's going to be difficult. Big solutions are usually a combination of different efforts because there are many different parts of the web development process. I've seen a company that use PHP for ALL their flow including the cron jobs' scripts. Some might say, that's crazy, why not use python or faster languages for backend jobs? But it worked for them up until they hit their bottleneck then they reiterate and revised.
The path toward the "holy grail" for the perfect "solution" is long. Crowd sourcing for this answer will also be difficult because many people have already took that journey and fought their holy war with themselves so they will generally give you their preferences up front.
Sorry for the round about way of saying: I think if you are at a point of asking question of what's out there other than PHP? Then you're at a good transitional stage. Congrats. Now your two (popular) choices are: Ruby/RoR and Python/Django. Go test out two sample projects and make it work from setting up to making it run. See which process you like the most and pick one. I don't think you will go wrong with either choices.
Oh, is there a site that you really like or look up to? Perhaps you can learn about their technology stack and give that a try :P
Again, sorry for the convoluted answer and good luck with your journey toward Web Dev nirvana :)