If you've been curious how one programming languages syntax matches with another then you should check out Hyperpolygot.
I was kind of amazed how close Javascript, PHP, Python, and Ruby are on a syntax level. It really seems that at a high level it maters more about the community and the ideals than the syntax when choosing a language. Granted every job requires a specific set of tools and this helps show how you can pick up another language easier.
The hardest part is finding a project that forces you to get outside your comfort zone and pick up a new language. I've tried all four and I feel most comfortable in PHP. I really do like the asynchrony of Javascript/Node and it feels a little closer to PHP than the other two. I don't have that much experience with Ruby and Python however outside of just hacking around. I do feel it is easy to jump from one language to another and be able to work your way through it. Even if you're not extremely efficient from the get go.
Definitely check out check out Hyperpolygot it is really interesting.