PHP seemed cool back when I didn't know how to make websites. It gave me this false sense of confidence that making websites was simple. Then I grew up.
I'd love to use the alternatives but I think Ruby sucks too, I like it when data type rules are enforced at compile time instead of runtime. No matter how you design a website you will have to enforce data type rules somewhere, why not knock it out before the code even runs?
I'd wish Perl was an alternative, but honestly I think it sucks more. It's a better procedural language but that OOP soup is a nightmare. No thank you.
I'd wish C# was an option, but I don't want to pay MS that much money. I don't see the value in locking myself in to their technology. No thank you.
I'd wish C++ was an option. I absolutely love C++, unfortunately it can also be incredibly tedious at times. I would use C++ if there was a modern and well established web library for it, but I'm afraid I'll be stuck on my own trying reinvent wheels because of missing documentation. Furthermore, there goes any chance of collaboration. Most programmers aren't sharp enough for C++.
This is why I use Java. I am not a fan of Java and I think it's libraries suck, and it's implementation of generics without static typing support is backwards, but it's modern. Unfortunately, compared to PHP the setup is much much more complex and your hosting options are severely limited.
People use PHP because it's easy and it gives you the illusion that works just long enough for you to buy it.