Along the years I have come to admire more and more those who take what they do know and put the effort into just that: building something.
The idea of purpose is key here.
Once you have a purpose, a goal, finding the right tool for the job is no longer that difficult and you will suddenly realise that a lot the languages/frameworks people have been evangelising to you may make no sense at all.
"If you don’t know where you’re going, any road will get you there." - Lewis Carroll
The point is that getting started is the most important thing, and moving forward is the next most important thing. I'm not saying if someone comes to you and says, "I want to build a web app" one should say, "Do it in PHP." But if someone says, "I'm building my first web app in PHP" the most damaging thing you could say is, "lol you're coding like a noob. You should be doing that in {language x}."
I see happening all the time. Coding in PHP is better than not coding because you're terrified of not doing things "the right way," and that often is the alternative. Let him or her finish a project in PHP before you try to turn the ship around and make him or her learn Rails. Or JavaScript or Python, or Java or whatever. Just start.