Andrew Podner has posted an introduction to a concept in PHP that may not be easy to immediately grasp for someone relatively new to the language - the idea of lambdas and closures.

Beginning with PHP 5.3, the anonymous function, became available to developers as a means of improving flexibility and increasing the number of tools at our fingertips to build powerful PHP applications. What I have been seeing a lot of as I read through documentation is more frequent use of terms like lambda, closure, or anonymous function, and sometime the terms are often used interchangeably, so let’s take a deeper look into what all of these things are and what differences, if any, there are between them.

The post looks at lambdas first, defining them as "functions without names" that can be assigned to objects or called inline when needed. Next is closures, and it's noted that, in PHP, there's really not much difference. They both also allow for use of the "use" statement to import values into the function's local scope. He mentions the "$this" update that came in PHP 5.4 and includes some arguments against their use too.