Anonymous functions in PHP

With the release of version 5.3.0, PHP development team incorporated what are called anonymous functions or closure.

An anonymous function, as its name implies, is nothing more than a function that has no name and that can be used as a callback allowing greater elegance and readability of source code, it is also possible to assign an anonymous function to a variable as were another data PHP type. PHP internally converts this variable in an instance of the Closure class.