PHP中3种生成XML文件方法的速度效率比较

private function directWriteXml(&$data){
  $xmltext='<?xml version="1.0" encoding="UTF-8" ?>';
  $xmltext .='<DocumentData>';
  $xmltext .='<Detail>';
  $loop=count($data);
  foreach ($data as $d){
   $xmltext .=" <Row ID=\" {$d['id']} \"  Name=\" {$d['name']}\" />";
  }
  $xmltext .='</Detail>';
  $xmltext .='</DocumentData>';
  return $xmltext;
 }
 private function useDomDocument(&$data){
  //  创建一个XML文档并设置XML版本和编码。。
  $dom=new DomDocument('1.0', 'utf-8');
  //  创建根节点
  $detail01 = $dom->createElement('Detail');
  $dom->appendchild($detail01);
  foreach ($data as $d) {
      $row = $dom->createElement('Row'," ID=\" {$d['id']} \"  Name=\" {$d['name']}\" " );
      $detail01->appendchild($row);
  }
  return $dom->saveXML();
 }
 private function useSimpleXML(&$data){
  //  创建一个XML文档并设置XML版本和编码。。
  $string = <<<XML
<?xml version='1.0' encoding='utf-8'?>
<detail01>
</detail01>
XML;
  $xml = simplexml_load_string($string);
  foreach ($data as $d) {
      $xml->addChild('Row'," ID=\" {$d['id']} \"  Name=\" {$d['name']}\" " );
  }
  return $xml->asXML(); ;
 }

 $loop=10000;
  $xml='';
  switch($_GET['id']){
   case 1:
     $ts=$this->microtime_float();
     for( $i=0; $i<$loop; $i++)
      $xml=$this->directWriteXml($depdata);
     $te=$this->microtime_float();
     $t=$te-$ts;
     $this->assign('times',$t);
     $this->assign('method','直接写');
     break;
   case 2:
     $ts=$this->microtime_float();
     for( $i=0; $i<$loop; $i++)
      $xml=$this->useDomDocument($depdata);
     $te=$this->microtime_float();
     $t=$te-$ts;
     $this->assign('times',$t);
     $this->assign('method','DomDocument');
     break;
   case 3:
     $ts=$this->microtime_float();
     for( $i=0; $i<$loop; $i++)
      $xml=$this->useSimpleXML($depdata);
     $te=$this->microtime_float();
     $t=$te-$ts;
     $this->assign('times',$t);
     $this->assign('method','SimpleXML');
     break;
  }
  echo $xml;