通过PHP函数从XML删除元素时出错

Question

I am trying to Delete a user with particular ID from an xml file but facing following error:

Argument 1 passed to DOMNode::removeChild() must be an instance of DOMNode, null given in delUser.php

XML file:

<currentUsers>  
<user id="101" firstName="Klashinkof" p2p="Yes" priority="Low"/>    
<user id="102" firstName="John" p2p="Yes" priority="High"/> 
</currentUsers>

code:

  <?php
     $id=101; //Test

// SETUP $doc
$doc = new DomDocument("1.0");
$doc->preserveWhiteSpace = FALSE;
$doc->validateOnParse = true; 
$doc->Load('currUsers.xml');

//REMOVE ID
    $user= $doc->getElementByID($id);
    $users= $doc->documentElement;

    if ($oldPerson = $users->removeChild($user)) {
        // worked
        echo "DELETED user {$id}";
        } else {
        return "Couldn't remove $id listing";
    }
$doc->save(curr.xml); 
?>

Answer 1

Your

$doc->getElementById($id);

returns NULL . You do not have a schema or DTD attached, so the id attribute is not a valid ID attribute in the XML sense. Thus, it cannot be found by getElementById . In addition, IDs may not start with a digit.

Either use XPath, eg

$xp = new DOMXPath($doc);
$node = $xp->query("//*[@id='$id']")->item(0);

or change the id attribute to xml:id , but then you will also have to use a valid ID attribute value.

Once you fetched the node, the easiest way to remove it is to fetch the parentNode from it, eg

$node->parentNode->removeChild($node);

Further details in Simplify PHP DOM XML parsing - how?

Answer 2

getElementByID() take a string as parameter as shown on the manual .

So it should be $id="101";

Plus, you should have a check before using removeChild() like if(!is_null($user)){...}

@Gordon's solution is faster but if you don't understand XPATH (which you should learn), you can use this :

$users = $doc->getElementsByTagName('user');
foreach($users as $user){
   if($user->hasAttribute('id') && $user->getAttribute('id') == $id){
      $user->parentNode->removeChild($user);
   }
}

DEMO HERE