I'm taking care of this by memoizing them, at least when using Fn::lambda() to create a function with create_function. However, the whole return function() {};

I'm taking care of this by memoizing them, at least when using Fn::lambda() to create a function with create_function. However, the whole return function() {}; should be garbage collected, since internally it's creating an object of type Closure with a magic method __invoke(). It's really quite the hack from what I've seen.