PHP5 supports XML natively in certain extent. The usage is demonstrated as follows in a number of examples:

Create XML content

// Create a DOM
$dom = new DomDocument('1.0');
// Create root node
$root = $dom->appendChild($dom->createElement('books'));
// Create sub-node
$sub = $root->appendChild($dom->createElement('book'));
// Add text node
$sub->appendChild($dom->createTextNode('Foo Bar')); 
// Generate xml 
$dom->formatOutput = true;
$xmlContent = $dom->saveXML();  // save to a variable
$dom->save('file.xml');         // save to a file

Imports XML from string variable

$xmlStr = <<<XML
  <book>Foo bar</book>
  <book><title>Blah</title><author>John Doe</author></book>
  <book type="draft">Foo bar</book>
$xml = new SimpleXMLElement($xmlStr); 

echo $xml->book[0]; // Foo bar
echo $xml->book[1]->author; // John Doe
echo (string) $xml->book[2]['type']; // draft, casting to string is required

// Process by a loop
foreach ($xml->book as $book) {

// Adding nodes
$book = $xml->addChild("book");
$book->addChild("title","A Title of a Book");

// Output
echo $xml->asXML();