格式参考  http://zhanzhang.baidu.com/wiki/44 

function makeXML(){
   $content='<?xml version="1.0" encoding="UTF-8"?>
   <urlset
    xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9
    http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd">
   ';
   $data_array=array(
    array(
     'loc'=>'http://www.phpernote.com/',
     'priority'=>'1.0',
     'lastmod'=>'2012-06-03T04:20:32-08:00',
     'changefreq'=>'always',
    ),
    array(
     'loc'=>'http://www.phpernote.com/php/',
     'priority'=>'0.5'