PHP: how to evaluate a function as a parameter?

The code {code...} is not very reliable, and $ variable is difficult to distinguish between string and function.

This code is not very reliable. I feel that $ variable is difficult to distinguish between string and function.

Reply content:

This code is not very reliable. I feel that $ variable is difficult to distinguish between string and function.

Anonymous Functions

function f1(callable $f){    return function ($iterator) use ($f){            return $f($iterator);        };}

If you want to determine$varWhether it is a function (to be accurate, whether it can be called), you can useis_callable($var)This function is used for judgment. Or directly usefunction foo(callable $function).

Determine whether a function exists

Function foo ($ function) {if (! Function_exists ($ function) {die ('Do not have this function');} $ function ("World ");}