CODEWITHSUNDEEP
phpxmldom
liewl
liewl

Reputation: 4051

Problems with deleting XML elements using PHP DOM

Here's the XML file i'm working on:

<list>
    <activity>swimming</activity>
    <activity>running</activity>
    <activity>soccer</activity>
</list>

The index.php, page that shows the list of activities with checkboxes, a button to delete the checked activities, and a field to add new activities:

<html>
<head></head>
<body>
<?php
    $xmldoc = new DOMDocument();
    $xmldoc->load('sample.xml', LIBXML_NOBLANKS);

    $count = 0;

    $activities = $xmldoc->firstChild->firstChild;
    //prints the list of activities, with checkboxes on the left for each item
    //the $count variable is the id to each entry
    if($activities!=null){
        echo '<form name=\'erase\' action=\'delete.php\' method=\'post\'>' . "\n";
        while($activities!=null){
            $count++;
            echo "    <input type=\"checkbox\" name=\"activity[]\" value=\"$count\"/>";
            echo ' '.$activities->textContent.'<br/>'."\n";
            $activities = $activities->nextSibling;
        }
        echo '    <input type=\'submit\' value=\'erase selected\'>';
        echo '</form>';
    }
?>
//section used for inserting new entries. this feature is working as expected.
<form name='input' action='insert.php' method='post'>
    insert activity:
    <input type='text name='activity'/>
    <input type='submit' value='send'/>
    <br/>
</form>
</body>
</html>

the delete.php, which is not working as expected:

<?php
    $xmldoc = new DOMDocument();
    $xmldoc->load('sample.xml', LIBXML_NOBLANKS);

    $atvID = $_POST['activity'];

    foreach($atvID as $id){
        $delnode = $xmldoc->getElementsByTagName('activity');
        $xmldoc->firstChild->removeChild($delnode->item($id));
    }

    $xmldoc->save('sample.xml');
?>

I've tested the deletion routine without the loop, using an hard-coded arbitrary id, and it worked. I also tested the $atvID array, and it printed the selected id numbers correctly. When it is inside the loop, here's the error it outputs:

Catchable fatal error: Argument 1 passed to DOMNode::removeChild() must be an instance of DOMNode, null given in /directorypath/delete.php on line 9

What is wrong with my code?

Upvotes: 2

Views: 6756

Answers (3)

John ODonnell
John ODonnell

Reputation: 21

The tricky thing about DOMNodeLists is that they are NOT arrays. If you delete a node, the list will re-index. This will cause your code to break if a user selects more than one item for deletion. If you selected swimming and running, swimming and soccer would be deleted.

You might want to start by giving each activity a unique identifier you can search for, say an attribute called 'id' (this likely wouldn't be a real ID. The DOM's getElementByID() only works for XML that has a DTD, like an HTML page. I'm guessing you don't want to go there.)

You might update you're XML to look like this.

<list>
    <activity name="swimming">swimming</activity>
    <activity name="running">running</activity>
    <activity name="soccer">soccer</activity>
</list>

You'd use these name attributes instead of $count as the value inside your checkboxes.

You can then use xPath to find items to remove inside your foreach.

$xpath = new DOMXPath($xmldoc);
$xmldoc->firstChild->removeChild($xpath->query("/list/activity[@name='$id']")->item(0));

Hope this helps get you started.

Upvotes: 1

david
david

Reputation: 691

In addition to moving $count++ to the end of the while loop, it might be a good idea to have delete.php check to make sure the $_POST['activity'] is numeric and within the specified range, just to ensure there are no fatal error messages generated on your page.

Upvotes: 1

Czimi
Czimi

Reputation: 2534

the DOMNodeList items are indexed starting with 0; You need to move the $count++ to the end of the while loop in the output step.

Upvotes: 2

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