How should class MyObject be defined for the following code to work properly?

Zend 200-550 Question Answer

How should class MyObject be defined for the following code to work properly? Assume $array is an array and MyObject is a user-defined class.

$obj = new MyObject();

array_walk($array, $obj);

MyObject should extend class Closure

MyObject should implement interface Callable

MyObject should implement method __call

MyObject should implement method __invoke

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