Question

I’m looking at this example array_filter comment and he passes an argument to array_filter as

array_filter($subject, array(new array_ereg("image[0-9]{3}\.png"), 'ereg')

How is it that the callback accepts an array with multiple arguments one of them being the actual callback function

Answer 1

In PHP it is possible to represent a callable using an array in the following format.

array($object, 'methodName')

The documentation itself states:

A method of an instantiated object is passed as an array containing an object at index 0 and the method name at index 1.

It is quite common to see this used with the $this variable inside objects.

In your example, the first element of the array is created with new, and is the instantiated object required, and ereg is the method.