Those still trying to get a handle on anonymous functions, lambdas and closures in the recently released 5.3 version of PHP might want to take a look at this new tutorial from the Recess blog. It's the first part of their "Functional PHP 5.3" series.
One of the most exciting features of PHP 5.3 is the first-class support for anonymous functions. You may have heard them referred to as closures or lambdas as well. There's a lot of meaning behind these terms so let's straighten it all out.
They explain the differences between closures and lambda functions (hint: not much) and give code examples for both them and closures.