Adding child nodes using SimpleXML

Question

Hello all. I have an XML document and want to insert a new node at a specific spot using SimpleXML.

The original XML is this:

<epp 
  xmlns="urn:ietf:params:xml:ns:epp-1.0" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="urn:ietf:params:xml:ns:epp-1.0 epp-1.0.xsd"
>
  <command>
    <create>
      <domain:create 
        xmlns:domain="urn:ietf:params:xml:ns:domain-1.0"
        xsi:schemaLocation="urn:ietf:params:xml:ns:domain-1.0 domain-1.0.xsd"
      >
        <domain:period unit="y"></domain:period>
      </domain:create>
    </create>
  </command>
</epp>

after <domain:create> I need to add the following node:

<domain:ns>
  <domain:hostAttr>
    <domain:hostName></domain:hostName>
    <domain:hostAddr ip="v4"></domain:hostAddr>
  </domain:hostAttr>
</domain:ns>

How can I do that? I have tried this:

$xmlObj = simplexml_load_file('myXMLFile.xml');
$nsNode = $xmlObj->command->create->children(self::OBJ_URI_DOMAIN)->create->addChild('domain:ns');
$hostAttr = $nsNode->addChild('domain:hostAttr');
$hostName = $hostAttr->addChild('domain:hostName');
$hostAddr = $hostAttr->addChild('domain:hostAddr');
$hostAddr->addAtribute('ip', 'v4');

On this first line, I'm getting this warning:

Warning: SimpleXMLElement::addChild() [simplexmlelement.addchild]: Cannot add child. Parent is not a permanent member of the XML tree

On the second line, and because of this, I'm getting:

Fatal error: Call to a member function addChild() on a non-object

Thanks in advance.

Additional notes: - The php version is higher then 5.1; - I have successfully added child nodes later on this same XML.

Answer 1

You want the child added to <create>.

$nsNode = $xmlObj->command->create->addChild('domain:ns');

The children() method returns a filtered list of child nodes. This list is - just as the error message indicates - not a permanent member of the document tree, it cannot be added to.

Adding a child works on the respective parent element only, or the operation would not be called "addChild", but "addSibling" - and this is not how the concept of the DOM works.

PS: Your second error message ("Call to a member function on a non-object") is the result of regular sloppiness. You can't just use an object without checking that it is actually there, your code lacks this check:

if ($nsNode !== null) {
  $hostAttr = $nsNode->addChild('domain:hostAttr');
  $hostName = $hostAttr->addChild('domain:hostName');
  $hostAddr = $hostAttr->addChild('domain:hostAddr');
  $hostAddr->addAttribute('ip', 'v4');
} else {
  echo "Oops, addChild() failed!";
}

Answer 2

I cannot reproduce the first error

<?php
echo phpversion(), "\n";
// $xmlObj = simplexml_load_file('myXMLFile.xml');
$xmlObj = getDoc();

$nsNode = $xmlObj->command->create->children('urn:ietf:params:xml:ns:domain-1.0')->create->addChild('domain:ns');
$nsNode->addChild('foo', 'Mary had a little lamb...');
echo $xmlObj->asxml();

function getDoc() {
  return new SimpleXMLElement('<epp 
    xmlns="urn:ietf:params:xml:ns:epp-1.0" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="urn:ietf:params:xml:ns:epp-1.0 epp-1.0.xsd"
  >
    <command>
      <create>
        <domain:create 
          xmlns:domain="urn:ietf:params:xml:ns:domain-1.0"
          xsi:schemaLocation="urn:ietf:params:xml:ns:domain-1.0 domain-1.0.xsd"
        >
          <domain:period unit="y"></domain:period>
        </domain:create>
      </create>
    </command>
  </epp>');
}

prints

5.3.2
<?xml version="1.0"?>
<epp xmlns="urn:ietf:params:xml:ns:epp-1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:ietf:params:xml:ns:epp-1.0 epp-1.0.xsd">
    <command>
      <create>
        <domain:create xmlns:domain="urn:ietf:params:xml:ns:domain-1.0" xsi:schemaLocation="urn:ietf:params:xml:ns:domain-1.0 domain-1.0.xsd">
          <domain:period unit="y"/>
        <domain:ns><domain:foo>Mary had a little lamb...</domain:foo></domain:ns></domain:create>
      </create>
    </command>
  </epp>