Closures in PHP… what, precisely, are they and when would you need to use them?

Question

So I\'m programming along in a nice, up to date, object oriented fashion. I regularly make use of the various aspects of OOP that PHP implements but I am wondering when might I

Answer 1

Apart from the technical details, closures are a fundamental pre-requisite for a programming style known as function oriented programming. A closure is roughly used for the same thing as you use an object for in object oriented programming; It binds data (variables) together with some code (a function), that you can then pass around to somewhere else. As such, they impact on the way that you write programs or - if you don't change the way you write your programs - they don't have any impact at all.

In the context of PHP, they are a little odd, since PHP already is heavy on the class based, object oriented paradigm, as well as the older procedural one. Usually, languages that have closures, has full lexical scope. To maintain backwards compatibility, PHP is not going to get this, so that means that closures are going to be a little different here, than in other languages. I think we have yet to see exactly how they will be used.