Updating existing element in XML with PHP

Question

Currently, im having this for appending data to my items file:

    $xmldoc = new DOMDocument();
    $xmldoc->load('ex.xml');


    $item= $xmldoc->createElement('item');

    $item->setAttribute('id', '100');
    $item->setAttribute('category', 'Fitness');
    $item->setAttribute('name', 'Basketball');
    $item->setAttribute('url', 'http://google.com');
    $item->setAttribute('description', 'This is a description');
    $item->setAttribute('price', '899');


    $xmldoc->getElementsByTagName('items')->item(0)->appendChild($item);
    $xmldoc->save('ex.xml');

Now before appending this, I would like to check for an existing element "item" that has the same attribute id value.

And if it does it should update that element with these new data.

Currently it just appends and doesnt check anything.

score 2 · Accepted Answer · 2011-12-14 23:25:45Z

2

$xmldoc = new DOMDocument();
$xmldoc->load('ex.xml');

$xpath = new DOMXPath($xmldoc);
$query = $xpath->query('/mainXML/items/item[@id = "100"]');

$create_new_node = false;
if($query->length == 0)
{
    $item = $xmldoc->createElement('item');
    $create_new_node = true;
}
else
{
    $item = $query->item(0);
}

$item->setAttribute('id', '100');
$item->setAttribute('category', 'Fitness');
$item->setAttribute('name', 'Basketball');
$item->setAttribute('url', 'http://google.com');
$item->setAttribute('description', 'This is a description');
$item->setAttribute('price', '899');

if($create_new_node)
{
    $xmldoc->getElementsByTagName('items')->item(0)->appendChild($item);
}
$xmldoc->save('ex.xml');

edited Dec 14, 2011 at 23:25

answered Dec 14, 2011 at 23:05

user142162

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5 Comments

Karem Over a year ago

Doesnt work, tried this and the query solution you just had - it just appends still

Karem Over a year ago

And it should be $xmldoc->getelementbyid, not $doc, but i fixed that still nothing

Karem Over a year ago

Still nothing, it just appends

user142162 Over a year ago

@Karem: It works for me, so you'd better post your XML file.

user142162 Over a year ago

@Karem: Fixed. I suggest you look into XPath, as it will help you a lot when dealing with XML.

DaOgre · Accepted Answer · 2011-12-14 23:05:23Z

1

I haven't used this functionality but looks like a good match for DOMDocument: Get Element By ID

If you get a matching element, edit it, and if not, post away.

answered Dec 14, 2011 at 23:05

DaOgre

2,10016 silver badges28 bronze badges

1 Comment

Francis Avila Over a year ago

getElementById will not work with xml unless it has a DTD which specifies which attributes are ID type

Francis Avila · Accepted Answer · 2011-12-14 23:30:20Z

If you have a DTD for this xml file that specifies that the "id" attribute is an ID type (i.e. its value is unique in a document and uniquely identifies its element), then you can use DOMDocument::getElementById().

Most likely, however, you do not have a DTD. In this case, you should just use XPath:

$xmldoc = new DOMDocument();
$xmldoc->load('ex.xml');

$xpath = new DOMXPath($xmldoc);
$results = $xpath->query('//items/item[@id=100][0]');

if (!$results->length) {
    $item= $xmldoc->createElement('item');
    $item->setAttribute('id', '100');
    $item->setAttribute('category', 'Fitness');
    $item->setAttribute('name', 'Basketball');
    $item->setAttribute('url', 'http://google.com');
    $item->setAttribute('description', 'This is a description');
    $item->setAttribute('price', '899');

    $xmldoc->getElementsByTagName('items')->item(0)->appendChild($item);
    $xmldoc->save('ex.xml');
}

You should also consider using SimpleXML for this task. The way this xml is structured and manipulated would probably be better-suited to SimpleXML.

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