I know a lot of jobs often require you to write in a different language than you're used to. Let's say you're a PHP programmer and you apply for a job, they love you, they hire you. However, one problem the stuff your new employer is building is in another language like Ruby or Java. How do you just switch languages? Is it hard? If you're a native PHP programmer, how comfortable would you be switching to Ruby? If you've done this in the past, how long did it take you to understand what was being done in the project? How long did it take for you to be able to write new code/edit old code comfortably in the new language?
If you are talking about programming then programming means are concept not a coding or syntax. It's little typical but not hard to switch.
Every programming has the same structure(or little different). So, in order to switch language, if you already knows some programming language, you just need to learn a new syntax and it would not take too long.
I code in many different languages.. In my experience, its not really hard to switch languages if you have a clear logic. As others said, you only need to know the syntax, logic is same all over. And learning syntax is not very tough, because well, loops are loops, conditions are conditions, arrays are arrays, variables are variables in every language. Once you know how to program, language is just a tool.