PHP's Immediate Function Invocation

In PHP, the Immediately Invoked Function Expression (IIFE) has a partial equivalence in PHP 7, as you can invoke a function immediately after its definition. However, PHP 5.x doesn't support this feature.

For PHP 7, an example would be:

(function() { echo "yes, this works in PHP 7.\n"; })();

For PHP 5.x, the closest approximation is:

call_user_func(function() { echo "this works too\n"; });

This usage allows you to execute code immediately without the need for global variables and functions, making it convenient for encapsulation and dependency injection.