array_map on collection with array interfaces?

The array_map() function doesn't support a Traversable as its array argument, so you would have to perform a conversion step:

array_map($fn, iterator_to_array($myCollection));

Besides iterating over the collection twice, it also yield an array that will not be used afterwards.

Another way is to write your own map function:

function map(callable $fn){    $result = array();    foreach ($this as $item) {        $result[] = $fn($item);    }    return $result;}

Update

Judging by your use-case it seems that you're not even interested in the result of the map operation; therefore it makes more sense to use iterator_apply().

iterator_apply($myCollection, function($obj) {    $obj->method1();    $obj->method2();    return true;});

array_map wants, as the name suggests, arrays. It's not called iterator_map after all. ;)

Apart from iterator_to_array(), which produces a potentially large temporary array, there's no trick to make iterable objects work with array_map.

The Functional PHP library has a map implementation which works on any iterable collection.

If you're not interested in creating a new array that is a function mapped over the original array, you could just use a foreach loop (because you implement Iterator).

foreach($item in $myCollection) {    $item->method1();    $item->method2();}

if you actually want to use map, then I think you'll have to implement your own. I would suggest making it a method on Collection, eg:

$mutatedCollection = $myCollection->map(function($item) {     /* do some stuff to $item */    return $item;});

I would ask yourself if you really want to use map or do you really just mean foreach