php实现将数组转换为XML的方法

<?php
class A2Xml {
 private $version = '1.0';
 private $encoding = 'UTF-8';
 private $root  = 'root';
 private $xml  = null;
 function __construct() {
  $this->xml = new XmlWriter();
 }
 function toXml($data, $eIsArray=FALSE) {
  if(!$eIsArray) {
   $this->xml->openMemory();
   $this->xml->startDocument($this->version, $this->encoding);
   $this->xml->startElement($this->root);
  }
  foreach($data as $key => $value){
 
   if(is_array($value)){
    $this->xml->startElement($key);
    $this->toXml($value, TRUE);
    $this->xml->endElement();
    continue;
   }
   $this->xml->writeElement($key, $value);
  }
  if(!$eIsArray) {
   $this->xml->endElement();
   return $this->xml->outputMemory(true);
  }
 }
}
$res = array(
 'hello' => '11212',
 'world' => '232323',
 'array' => array(
  'test' => 'test',
  'b' => array('c'=>'c', 'd'=>'d')
 ),
 'a' => 'haha'
);
$xml = new A2Xml();
echo $xml->toXml($res);