php生成xml文档有关问题

$data_array = array(  

    array(  

    'title' => 'title1',  

    'content' => 'content1',  

        'pubdate' => '2009-10-11',  

    ),  

    array(  

    'title' => 'title2',  

    'content' => 'content2',  

    'pubdate' => '2009-11-11',  

    )  

);  

  

//  属性数组  

$attribute_array = array(  

    'title' => array(  

    'size' => 1  

    )  

);  

  

$string = <<
  

  

  

XML;  

  

$xml = simplexml_load_string($string);  

  

foreach ($data_array as $data) {  

    $item = $xml->addChild('item');  

    if (is_array($data)) {  

        foreach ($data as $key => $row) {  

          $node = $item->addChild($key, $row);  

  

          if (isset($attribute_array[$key]) && is_array($attribute_array[$key]))  

            {  

              foreach ($attribute_array[$key] as $akey => $aval) {  

             //  设置属性值  

                  $node->addAttribute($akey, $aval);  

            }  

          }  

        }