How do I immediately execute an anonymous function in PHP?

Question

In JavaScript, you can define anonymous functions that are executed immediately:

(function () { /* do something */ })()

Can you do somethin

Answer 1

Note, accepted answer is fine but it takes 1.41x as long (41% slower) than declaring a function and calling it in two lines.

[I know it's not really a new answer but I felt it was valuable to add this somewhere for visitors.]

Details:

 function(){
                $f = function(){
                        $x = 123;
                };
                $f();
        },
        'test2_anonfunc_call_user_func' => function(){
                call_user_func(
                        function(){
                                $x = 123;
                        }
                );
        }
), 10000);
?>

Results:

$ php test8.php
test1_anonfunc_call took 0.0081379413604736s (1228812.0001172/s)
test2_anonfunc_call_user_func took 0.011472940444946s (871616.13432805/s)