// 创建SimpleXML对象
$xml = new SimpleXMLElement('<?xml version="1.0" encoding="UTF-8"?><root></root>');

// 添加元素
$xml->addChild('book');
$xml->book->addChild('title', 'PHP Programming');
$xml->book->addChild('author', 'John Doe');
$xml->book->addChild('year', '2023');

// 输出XML
header('Content-type: text/xml');
echo $xml->asXML();

// 保存到文件
$xml->asXML('books.xml');

// 创建DOMDocument对象
$dom = new DOMDocument('1.0', 'UTF-8');

// 格式化输出
$dom->formatOutput = true;

// 创建根元素
$root = $dom->createElement('books');
$dom->appendChild($root);

// 添加book元素
$book = $dom->createElement('book');
$root->appendChild($book);

// 添加子元素
$title = $dom->createElement('title', 'PHP Programming');
$book->appendChild($title);

$author = $dom->createElement('author', 'John Doe');
$book->appendChild($author);

$year = $dom->createElement('year', '2023');
$book->appendChild($year);

// 输出XML
header('Content-type: text/xml');
echo $dom->saveXML();

// 保存到文件
$dom->save('books.xml');

$xml = '<?xml version="1.0" encoding="UTF-8"?>';
$xml .= '<books>';
$xml .= '<book>';
$xml .= '<title>PHP Programming</title>';
$xml .= '<author>John Doe</author>';
$xml .= '<year>2023</year>';
$xml .= '</book>';
$xml .= '</books>';

// 输出XML
header('Content-type: text/xml');
echo $xml;

// 保存到文件
file_put_contents('books.xml', $xml);

$description = 'This is <b>bold</b> & "important"';
$escaped = htmlspecialchars($description, ENT_XML1, 'UTF-8');

$xml->book->addAttribute('id', '123');

$book->setAttribute('id', '123');

// SimpleXML
$xml->book->addChild('description')->addCData('Some <b>HTML</b> content');

// DOMDocument
$cdata = $dom->createCDATASection('Some <b>HTML</b> content');
$description = $dom->createElement('description');
$description->appendChild($cdata);
$book->appendChild($description);

// SimpleXML
$xml->addChild('ns:element', 'value', 'http://example.com/ns');

// DOMDocument
$element = $dom->createElementNS('http://example.com/ns', 'ns:element', 'value');