I'm going to reveal my ignorance here, but in my defense, I'm an accounting major, and I've never taken a computer science class.
I'm about to start a new project, and I'm considering using Python instead of PHP, even though I am much more adept with PHP, because I have heard that Python is a more powerful language. That got me wondering, what makes one programming language more powerful than another? I figure javascript isn't very powerful because it (generally) runs inside a browser. But, why is Python more powerful than PHP? In each case, I'm giving instructions to the computer, so why are some languages better at interpreting and executing these instructions? How do I know how much "power" I actually need for a specific project?
I would not say that there are computer languages "more powerful", just languages more suited for your specific problem domain.
That said, PHP is a language that evolved from a hack and tailored for a very specific problem domain; this shows up in several places, like for example inconsistent parameter order across database interfaces. IMHO PHP community has made some very sad decisions for new syntax enhancements over the time.
IMHO Python is much more general, well designed and elegant, but your question is one that usually starts flamewars.
What makes some programming languages more powerful than others?