Is it possible to learn two programming languages at the same time?

I think you should stick to one language at a time; and, if you don't, make sure you have been using one of the languages for a while. I remember when I wanted to learn Java and JavaScript, there was just one problem: I wanted to learn them both at the same time.

Please be smart about this; I think it might come back and cause some problems later on.

I'd imagine it would be overwhelming, because syntax aside, there are general programming concepts that take time to grasp. I think maybe once you've got a good handle on one language, what you're talking about might be a bit easier, though. And maybe you're a super-genius who would have no trouble with it at all, but I'm definitely not, so I'd take it one at a time and ensure that I fully understood every part. That's just my opinion though, and I'm by no means an expert on the matter. I think it could be doable, but I would recommend sticking to one :)

It's probably possible, but also depends on what you mean when you say "learn". In any case, I would advise to go one at a time, especially since Java and Javascript are quite different (despite the name similarity). I personally know only the very basics of Javascript, while I've gone really deep with the Java courses on Treehouse (both in Java Web Development and Android tracks). And I did know some Java prior to all this, so my intention is to get as much as I can at first with the language I am most familiar with.

And it's a productive path, I got to strengthen and upgrade my Java skills, and in the meantime learn some common design patterns used in software development in the language I'm most familiar with, making them easier to grasp. And I'm pretty sure most of those design patterns are easily transferable to other languages. I also plan to take on some front end courses at a later time (because HTML/CSS/Javascript can always come in handy), but not until I go through all (or most) of the Java content first.

Yes it is possible. But if you want to go this way I would recommend learning one language at a time. For example if you learn c# or java first, you will have a less difficult time learning PHP because they use fairly the same concepts, but in a different way. Get familiar with one language, learn their syntax and code designs and then continue learning a different language.

I'd absolutely say it's possible, but if you're learning two languages at once, make sure you're giving them each enough attention. Do a little of both languages every day, or alternate days, but don't take too long of a break or the syntax from one will start to replace the other in your brain. I've been learning JavaScript and Python simultaneously, and I'm constantly mixing up things like string.length (JavaScript) and len(string) (Python). I think it is a really good mental exercise to practice multiple languages at once, and it certainly improves your debugging and Google-Fu.