php DOMDocument 创建，加载，解析xml文档代码

$xml_str = "<?xml version='1.0'?>";
$xml_str .= "<books>";
$xml_str .= "<book>";
$xml_str .= "<title>harry potter</title>";
$xml_str .= "<author>j.k.rowling</author>";
$xml_str .= "<publisher>warner bros.</publisher>";
$xml_str .= "<price>39.0</price>";
$xml_str .= "</book>";
$xml_str .= "</books>";

$dom = new domdocument;
$dom->loadxml($xml_str);

echo $dom->savexml();
$dom->save("test.xml");

//domdocument 加载xml文档

$dom = new domdocument;

$dom->load('17-1.xml');
$root = $dom->documentelement;

$doc = new domdocument();
$doc->load("17-1.xml");

$books = $doc->getelementsbytagname("book");
foreach($books as $book)
{
    $authors = $book->getelementsbytagname("author");
    $author = $authors->item(0)->nodevalue;
   
    $publishers = $book->getelementsbytagname("publisher");
    $publisher = $publishers->item(0)->nodevalue;
   
    $titles = $book->getelementsbytagname("title");
    $title = $titles->item(0)->nodevalue;
   
    $prices = $book->getelementsbytagname("price");
    $price = $prices->item(0)->nodevalue;
   
    echo "$title - $author - $publisher - $price";
    echo "<br/>";
    echo "<br/>";
}

class rss {
   //public
   $rss_ver = "2.0";
   $channel_title = '';
   $channel_link = '';
   $channel_description = '';
   $language = 'zh_cn';
   $copyright = '';
   $webmaster = '';
   $pubdate = '';
   $lastbuilddate = '';
   $generator = 'redfox rss generator';

   $content = '';
   $items = array();

   function rss($title, $link, $description) {
       $this->channel_title = $title;
       $this->channel_link = $link;
       $this->channel_description = $description;
       $this->pubdate = date('y-m-d h:i:s',time());
       $this->lastbuilddate = date('y-m-d h:i:s',time());
   }

   function additem($title, $link, $description ,$pubdate) {
       $this->items[] = array('titile' => $title ,
                        'link' => $link,
                        'description' => $description,
                        'pubdate' => $pubdate);
   }

   function buildrss() {
       $s = "<!--l version="1.0" encoding="gb2312"--> ";
       // start channel
       $s .= " ";
       $s .= " "
       $s .= "<link />{$this->channel_link} ";
       $s .= "{$this->channel_description} ";
       $s .= "{$this->language} ";
       if (!empty($this->copyright)) {
          $s .= "{$this->copyright} ";
       }
       if (!empty($this->webmaster)) {
          $s .= "{$this->webmaster} ";
       }
       if (!empty($this->pubdate)) {
          $s .= "{$this->pubdate} ";
       }

       if (!empty($this->lastbuilddate)) {
          $s .= "{$this->lastbuilddate} ";
       }

       if (!empty($this->generator)) {
          $s .= "{$this->generator} ";
       }
     
       // start items
       for ($i=0;$iitems),$i++) {
           $s .= " ";
           $s .= " ";
           $s .= "<link />{$this->items[$i]['link']} ";
           $s .= "<!--data[{$thi-->items[$i]['description']}]]> ";
           $s .= "{$this->items[$i]['pubdate']} ";         
           $s .= " ";
       }
    
      // close channel
      $s .= " ";
      $this->content = $s;
   }

   function show() {
       if (empty($this->content)) $this->buildrss();
       header('content-type:text/xml');
       echo($this->content);
   }

   function savetofile($fname) {
       if (empty($this->content)) $this->buildrss();
       $handle = fopen($fname, 'wb');
       if ($handle === false)  return false;
       fwrite($handle, $this->content);
       fclose($handle);
   }
}

$root = $doc->createelement('book');
$root = $doc->appendchild($root);

$title = $doc->createelement('title');$title = $root->appendchild($title);

$text = $doc->createtextnode('this is the title');
$text = $title->appendchild($text);

echo "retrieving all the document: ";
echo $doc->savexml() . " ";

echo "retrieving only the title part: ";
echo $doc->savexml($title);