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Date: Thu, 12 Jul 2012 00:17:25 +0200
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To: PHP internals <internals@lists.php.net>
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Subject: Internal iteration API
From: nikita.ppv@gmail.com (Nikita Popov)

Hi internals!

Currently PHP does not have an internal iteration API that supports
both arrays and Traversable objects. Because of that it is currently
not really possible to write functions (or language features) that
work on arbitrary traversables. That's probably also the reason why
function like array_sum() currently work only on arrays and arrays
only.

So I'd really like to have such an API. One idea for an implementation
would be this:
 * Create a zend_create_iterator_from_zval() function, which returns a
zend_object_iterator
 * For arrays and plain objects this would create a thin wrapper
around the zend_hash_* iteration functions
 * For objects defining get_iterator this would just return the
object_iterator that get_iterator returned
 * Usage:

       zend_object_iterator *iter = zend_create_iterator_from_zval(zval);
       if (iter->rewind) iter->rewind(iter);
       while (iter->valid(iter)) {
           zval **value;
           iter->get_current_data(iter, &value);
           // do something
           iter->move_forward(iter);
       }
       iter->dtor(iter);

I like this approach because it reuses the existing
zend_object_iterator API. But I see that this is rather an abuse than
a use :)

Thoughts?

Nikita