Can't edit/save DOM XML Element Attribute using DomDocument

Question

I have an XML file like below. I have to use the DOMDocument, so no extra classes allowed. (note I have simplified it, the real file has many entries in both saleItems and catalogItems):

<?xml version="1.0"?>
<catalog>
    <saleItems count="3">

        <item name="Xbox 360 Wired Controller" price="19" stock="50" salePrice="12" onSale="yes">
            <image>Xbox360Controller.jpg</image>
            <description>A wired controller for an Xbox 360 Game Console. Comes in either white or black.</description>
        </item>

    </saleItems>

    <catalogItems count="12">
        <item name="Dell Alienware Laptop 15 inch" price="2500" stock="200" salePrice="0" onSale="no">
            <image>alienwareLaptop.jpg</image>
            <description>sample description here</description>
        </item>
    </catalogItems>
</catalog>

I need to do the following:

1) find the node to update based on the name="" attribute (ex: the only data I have to find the appropriate item is the item name)

2) when it is found, I need to edit the quantity attribute of just that item (subtract 1)

3) when the quantity has been updated, I need the XML file to be saved back to the server.

I'm at whits ends with this, I'm having a hard time getting the $domDocument to cooperate.. This is what I have so far, but it does not seem to work properly at all. I can get the stock and substract it, but my changes aren't being saved to the file.

foreach( $GLOBALS['catalogItems'] as $item ){
    if( $item->getAttribute('name') == $itemName ){
        // we have a match
        $oldStock = $item->getAttribute("stock");
        $item->setAttribute("stock", $oldStock + $modifier);

        $dom->save('xml/catalog.xml');
    }
}

any help much appreciated!

You shouldn't do the saving in the traversal loop. Also consider using Xpath in conjunction to DOMDocument. — mario
– mario, Commented Jan 28, 2013 at 3:22
@mario: thanks for the input! so should I save outside the foreach? also I cannot use Xpath -- this is a small part of a larger assignment for a class (before anyone asks yes SO usage is encouraged :) ), and the course unfortunately requires just the use of DOMDocument and XMLReader, both of which I am unfamiliar with. :( — tdc
– tdc, Commented Jan 28, 2013 at 3:24
Long shot: What's with the variable scope? I see you pull one from the global scope, but is $dom also present? Can you print_r($dom->saveHTML()); the DOM structure after the loop? Is that output updated? (The loop looks fine at first glance). Did you check for file permissions prior saving? (error_reporting? Add some debug statements, "$itemName found", print new calculation result, etc. — mario
– mario, Commented Jan 28, 2013 at 3:30
@mario: $dom is used throughougt the file (including in the global scope), but prior to the loop I defined $dom = new DomDocument() and loaded the catalog.xml file into it. when I echo saveHTML() after the loop it spints out the entire XML file in plaintext. — tdc
– tdc, Commented Jan 28, 2013 at 3:36

Community · Accepted Answer · 2021-01-18 12:34:40Z

1

Solved via PHP chat: https://chat.stackoverflow.com/transcript/message/7402294#7402294

The problem was that his selector for $GLOBALS['catalogItems'] included DOMText items, which would fail when calling $item->getAttribute('name'). The solution is to make sure $item is actually an item node and then to do the other checks if it an item.

edited Jan 18, 2021 at 12:34

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answered Jan 28, 2013 at 4:42

Levi Morrison

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1 Comment

tdc Over a year ago

Thanks so much to @Levi Morrison, helped me out in the chat. :)

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