Updating existing element in XML with PHP - 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.

Answer 1

$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');

Answer 2

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.

Answer 3

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.