php如何将数组转换成xml

$data = array(
  'name' => '小米',
  'age' => 30,
  'sex' => '男',
  'email' => 'ipkd@example.com'
);

function array_to_xml($data, $xml = null){
  if($xml === null){
    $xml = new SimpleXMLElement('');
  }
  foreach($data as $key => $value){
    if(is_array($value)){
      array_to_xml($value, $xml->addChild($key));
    }else{
      $xml->addChild($key, htmlspecialchars($value));
    }
  }
  return $xml->asXML();
}

$xml = array_to_xml($data);
echo $xml;