I've felt much the same for the last few years.
For me, it's about the (non-existent) ecosystem around PHP. Take a look at something like Ruby, it has a massive (almost cult like) following of good developers. There are so many more quality tools, and allot more people thinking outside of simple web development. Python is much the same.
In my eyes PHP hasn't had this for many years. Sure, there are probably more people still using PHP, but there are allot of poor PHP programmers. I really think that most of the good PHP developers have either left, or are just not that interested in communities outside of the few exceptional frameworks that are around.
Allot of this comes down to PEAR I think. PEAR is far to monolithic in my opinion. A nice singular repository to store libraries is a great idea, but why do those libraries really need to be made part of the singular PEAR project? Ruby has Gems, and anyone can create a Gem and besides the spec file and a few other requirements you can do what you like with a Gem. PEAR just isn't as flexible. On top of that is the fact that allot of PHP developers simply think that going to the command line to install something is just too hard.
It's a completely different attitude surrounding PHP when compared to Ruby or Python. And that, IMO, is why these two languages in particular are making allot of ground, and also one of the same reason node.js will make allot more ground over the next few years.
Would I ever declare I am giving up PHP? No, it would be hard to unlearn what I have learn't. Would I rather be using Ruby or Python? Yes.