Question

Using the following function:

function is_closure($t) { return ( !is_string($t) && is_callable($t)); }

Can this return true for anything else, than an anonymous closure function? If so, what would be the correct way to determine, if a variable is a closure?

Many thanks

Answer 1

The most deterministic way to check if a callback is an actual closure is:

function is_closure($t) {
    return $t instanceof \Closure;
}

All anonymous functions are represented as objects of the type Closure in PHP. (Which, coming back to above comment, happen to implement the __invoke() method.)