ArrayObject, getIterator();

arrayobject, php, spl

Solution

`ArrayObject` implements `IteratorAggregate` which allows you to return an iterator instead of implementing it. It's pretty straightforward. Assume you have a class wrapping an array, like

class Foo
{
    private $array = [1,2,3,4];
}

and you want to `foreach` over an instance of `Foo`, like this:

foreach (new Foo as $bar) {
    echo $bar; // outputs 1234
}

To achieve that you could add the `Iterator` interface but then you'd had to implement all the methods in the interface for the simple task of iterating the array inside the object. You dont want to duplicate that code over and over again whenever you need that functionality, especially since there already is an Iterator that does what you want. So instead of implementing `Iterator` you implement `IteratorAggregate`

class Foo implements IteratorAggregate
{
    private $array = [1,2,3,4];

    public function getIterator()
    {
        return new ArrayIterator($this->array);
    }
}

Now when you do the `foreach` PHP will use the Iterator returned from `getIterator` instead of the `Foo` instance itself allowing you to get the output 1234.

In case of `ArrayObject`, the point is simply for allowing you to `foreach` over the values in the `ArrayObject`. Of course, you can also call `getIterator` yourself, since it's public and then use returned Iterator directly.

Also note the ctor signature of `ArrayObject`:

public __construct (
    [ mixed $input 
    [, int $flags = 0 
    [, string $iterator_class = "ArrayIterator" 
]]] )

which notes which Iterator will be returned.

Problem

I am trying to understand what `getIterator()` is, I will explain: As I know `getIterator` is a method we call to include an external Iterator. The problem is getIterator include it's own methods the closes think looks the same is Iterator interface but it can't be an interface it can be class but i am trying to search it inside the SPL.php source code and didn't find any, maybe I'm making this more complicated than it's really is, I will be happy if some one can help me understand where it is at the SPL.php source code and what is it (class,etc). Thank you all and have a nice day.

Original source