Re: When is an array not an array?

On Mon, 30 Oct 2006 14:24:45 GMT, "Andrew C" <nonsense@xxxxxxxxxxxxxxx> wrote:

I've encountered what seems to me to be something of an oddity while playing
around with XML parsing in PHP, and I wondered if any of you might be able
to clear up my confusion...

Here's a little code:

$xmlDoc = new DOMDocument();
$xmlDoc->load('widget_data.xml');
$widgets = $xmlDoc->getElementsByTagName('widget');

My understanding was that '$widgets' is an array of elements,

Nope - it's a DOMNodeList object, that has support for PHP5 iterators, so you
can use it in a foreach loop.

and the
following 'foreach' iterates through that array (this works):

foreach ($widgets as $widget)
{
...
}

However, I get an error if I try to access '$widgets' using square-brackets,
e.g.:

$widget = $widgets[0];

(The error is: "Fatal error: Cannot use object of type DOMNodeList as
array".)

There you go.

PHP confirms that the first element of the 'array' has an index/key of '0'
with the following (or similar), but won't let me access it directly using
'$widgets[0]':

foreach ($widgets as $key => $widget)
{
echo("<p>" . $key . "</p>\n");
}

Does anyone have an explanation as to why a DOMNodeList can be accessed like
an array using 'foreach', but won't allow square-brackets to be used? What
exactly *is* a DOMNodeList?

Thanks for any help.

A.

PS. I am aware that DOMNodeLists have an 'item()' method with which nodes
within the list can be referred to via index, but my confusion still stands
as to why I can't simply use '[]'s.

PHP doesn't support overloading operators, which I believe would be required
for supporting [] on objects implementing the appropriate interface.

Would be a sensible extension to the current functionality, though - as you
point out, DOMNodeList acts almost the same as an array, but not quite close
enough.

Failing that, it'd be somewhat useful if DOMNodeList had a method to convert
itself into an actual array, but it doesn't seem to have that either.

--
Andy Hassall :: andy@xxxxxxxxxxx :: http://www.andyh.co.uk
http://www.andyhsoftware.co.uk/space :: disk and FTP usage analysis tool
.

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