SimpleXMLElement::addChild

To complete Volker Grabsch's comment, stating :
"Note that although addChild() escapes "<" and ">", it does not escape the ampersand "&"."

To work around that problem, you can use direct property assignment such as :

<?php
$xmlelement->value = 'my value < > &';
// results in <value>my value &lt; &gt; &amp;</value>
?>

instead of doing :

<?php
$xmlelement->addChild('value', 'my value < > &');
// results in <value>my value &lt; &gt; &</value> (invalid XML)
?>

See also: http://stackoverflow.com/questions/552957 (Rationale behind SimpleXMLElement's handling of text values in addChild and addAttribute)

HTH

Here is a class with more functions for SimpleXMLElement :

<?php
/**
 *
 * Extension for SimpleXMLElement
 * @author Alexandre FERAUD
 *
 */
class ExSimpleXMLElement extends SimpleXMLElement
{
    /**
     * Add CDATA text in a node
     * @param string $cdata_text The CDATA value  to add
     */
  private function addCData($cdata_text)
  {
   $node= dom_import_simplexml($this);
   $no = $node->ownerDocument;
   $node->appendChild($no->createCDATASection($cdata_text));
  }

  /**
   * Create a child with CDATA value
   * @param string $name The name of the child element to add.
   * @param string $cdata_text The CDATA value of the child element.
   */
    public function addChildCData($name,$cdata_text)
    {
        $child = $this->addChild($name);
        $child->addCData($cdata_text);
    }

    /**
     * Add SimpleXMLElement code into a SimpleXMLElement
     * @param SimpleXMLElement $append
     */
    public function appendXML($append)
    {
        if ($append) {
            if (strlen(trim((string) $append))==0) {
                $xml = $this->addChild($append->getName());
                foreach($append->children() as $child) {
                    $xml->appendXML($child);
                }
            } else {
                $xml = $this->addChild($append->getName(), (string) $append);
            }
            foreach($append->attributes() as $n => $v) {
                $xml->addAttribute($n, $v);
            }
        }
    }
}
?>

Want to continue the ampersand (&) chain problem.

Sometimes, you would want to assign  (=) addChild.
This trick will helps you to do this.

<?php
$webOrders = new SimpleXMLElement('<?xml version="1.0"?><WebOrders></WebOrders>');
$webOrder = $webOrders->addChild('WebOrder');
$product = $webOrder->addChild('Product');
$product[0] = 'T&M';
$product->addAttribute('price', 19.99);
$product->addAttribute('qty', 2);
var_dump($webOrders->asXML());
?>

OUTPUT would be:

<?xml version="1.0" encoding="UTF-8"?>
<WebOrders>
    <WebOrder>
        <Product price="19.99" qty="2">T&amp;M</Product>
    </WebOrder>
</WebOrders>

In the docs for google sitemaps it is required an element for mobile sitemaps that looks like this: <mobile:mobile/>

I used some time to figure out how to make it, but it is quite simple when understood.

$mobile_schema = 'http://www.google.com/schemas/sitemap-mobile/1.0';

//Create root element
$xml_mobile = new SimpleXMLElement('
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:mobile="'.$mobile_schema.'"></urlset>
');

//Add required children
$url_mobile = $xml_b_list_mobile->addChild('url');
$url_mobile->addChild('loc', 'your-mobile-site-url');
$url_mobile->addChild('mobile:mobile', null, $mobile_schema);

For this to work properly the attribute xmlns:mobile must be set in the root node, and then used as namespace(third argument) when creating the mobile:mobile child with null as value.

Note that although addChild() escapes "<" and ">", it does not escape the ampersand "&".

So addChild() is unsuited to handle user-defined input!

Instead, you will have to replace all "&" with "&amp;" before calling addChild().

Or, use htmlspecialchars() which also replaces other characters, but won't do any harm as addChild() won't replace those again.

The class below allows you to write CDATA and to add additional attributes.

<?php
class SimpleXMLElementExtended extends \SimpleXMLElement
{
    public function addChildWithCData($name, $value)
    {
        $child = parent::addChild($name);
        $element = dom_import_simplexml($child);
        $docOwner = $element->ownerDocument;
        $element->appendChild($docOwner->createCDATASection($value));
        return $child;
    }
}
?>

Example:
<?php
        $xml = new SimpleXMLElementExtended('<xml></xml>');
        $content = $xml->addChildWithCData('content', 'Title of the page');
        $content->addAttribute('id', 1);
        $content->addAttribute('enabled', 'true');

        // Output:
        // <xml>
        //   <content id="1" enabled="true"><![CDATA[Title of the page]]></content>
        // </xml>
?>