PHP中的闭包……确切地说，它们是什么?您何时需要使用它们?

So I'm programming along in a nice, up to date, object oriented fashion. I regularly make use of the various aspects of OOP that PHP implements but I am wondering when might I need to use closures. Any experts out there that can shed some light on when it would be useful to implement closures?So I'm programming along in a nice, up to date,