delete elements in xml?

Question

i've got some elements in a xml document i want to delete. so i want to create another xml document without those elements.

here is an example of how it looks like at the moment:

<entity id="1000070">
    <name>apple</name>
    <type>category</type>
    <entities>
        <entity id="7002870">
            <name>mac</name>
            <type>category</type>
            <entities>
                <entity id="7002907">
                    <name>leopard</name>
                    <type>sub-category</type>
                    <entities>
                        <entity id="7024080">
                            <name>safari</name>
                            <type>subject</type>
                        </entity>
                        <entity id="7024701">
                            <name>finder</name>
                            <type>subject</type>
                        </entity>
                    </entities>
                </entity>
            </entities>
        </entity>
        <entity id="7024080">
            <name>iphone</name>
            <type>category</type>
            <entities>
                <entity id="7024080">
                    <name>3g</name>
                    <type>sub-category</type>
                </entity>
                <entity id="7024701">
                    <name>3gs</name>
                    <type>sub-category</type>
                </entity>
            </entities>
        </entity>
        <entity id="7024080">
            <name>ipad</name>
            <type>category</type>
        </entity>
    </entities>
</entity>

i want to create another xml document without the sub-category and subject elements.

so the new one will look like this:

<entity id="1000070">
    <name>apple</name>
    <type>category</type>
    <entities>
        <entity id="7002870">
            <name>mac</name>
            <type>category</type>
        </entity>
        <entity id="7024080">
            <name>iphone</name>
            <type>category</type>
        </entity>
        <entity id="7024080">
            <name>ipad</name>
            <type>category</type>
        </entity>
    </entities>
</entity>

should i use simplexml/php or xslt to do this? are there other ways?

would be great with some code examples...thanks!

Answer 1

I'd suggest using PHP's DOMDocument class and related classes (if only because I've been using this since forever. Don't really know if simplexml is better or not).

You would do the following:

$doc = new DOMDocument();
$doc->load($xml);
$rootNode = $doc->documentElement;
$entitiesNode = $rootNode->getElementsByTagName('entities')->item(0);
$entityNodes = $entitiesNode->getElementsByTagName('entity');

for($i = 0; $i < $entityNodes->length; $i++)
{
   $entityNode = $entityNodes->item($i);
   $subEntitiesNode = $entityNode->getElementsByTagName('entities');
   if($subEntitiesNode->length)
   {
       $subEntitiesNode->removeChild($subEntitiesNode->item(0));
   }
}

Note that i just wrote that from the top of my hat, so please don't sue if it doesn't work, but it should be reasonably close.
Apart from that, in order to find the nodes to be deleted in a more elegant way, have a look at the PHPs DOMXPath object.

Answer 2

One way is to define the XPath expression that selects the nodes you want to remove then use DOM to grab each node's parent and remove said node. SimpleXML doesn't have an easy way to do that.

For that kind of complicated manipulations, I use SimpleDOM.

include 'SimpleDOM.php';
$entity = simpledom_load_file('/path/to/your/file.xml');

// either delete all "subject" and "sub-category"
$entity->deleteNodes('//entity[type="subject" or type="sub-category"]');

// or remove everything but "category"
$entity->deleteNodes('//entity[not(type="category")]');

// remove empty <entities/>
$entity->deleteNodes('//entities[count(child::*) = 0]');

echo $entity->asXML();

Answer 3

Here some useful functions I use

/* ***** XML MANIPULATION FUNCTIONS ********* */
/**
Adds a new element in a XML list. 
Add $xnew after $x in $docm. 
*/
function XMLadd(DOMDocument $docm, DOMNode $x=null, DOMNode $newx=null, $mode=''){
    if($x!=null && $newx!= null){   
        if($mode === "a_") {
            if($x->nextSibling) {
                $x->parentNode->insertBefore( $docm->importNode($newx, true), $x->nextSibling);
            } else {
                $x->parentNode->appendChild( $docm->importNode($newx, true));
            }
        } else {
            $x->parentNode->insertBefore( $docm->importNode($newx, true), $x);
        }
    }
}

/**
Removes an element from a XML list. 
Remove $x, $x must be DOMNode in a DOMDocument  
*/
function XMLremove(DOMNode $x=null) {
    if($x!=null) {  
        //remove item
        $x->parentNode->removeChild( $x );
    }
}

/**
Replace an element in a XML List.
Parameters: $x(DOMNode) will be replaced by $newx(DOMNode) in $docm (DOMDocument)
*/
function XMLreplace(DOMDocument $docm, DOMNode $x=null, DOMNode $newx=null) {
    if($x!=null && $newx!= null) {  
        //replace = add + remove
        //add new element
        XMLadd($docm, $x, $newx);
        //remove item
        XMLremove($x);
    }
}

Answer 4

This works for your sample, but it may be a bit too much of a loose cannon.

$doc = new DOMDocument();
$doc->loadXML($xml);
$xpath = new DOMXPath($doc);

foreach ($xpath->query('entities/entity/entities') as $elem) {
    $elem->parentNode->removeChild($elem);
}