今天看到一个很好的类-操作xml的！

<?
/*
 (c) 2000 Hans Anderson Corporation. All Rights Reserved.
 You are free to use and modify this class under the same
 guidelines found in the PHP License.

 -----------

 bugs/me:
 http://www.hansanderson.com/php/
 me@hansanderson.com
 showstv@163.com

 -----------

 Version 1.0

 - 1.0 is the first actual release of the class. It's
 finally what I was hoping it would be, though there
 are likely to still be some bugs in it. This is
 a much changed version, and if you have downloaded
 a previous version, this WON'T work with your existing
 scripts! You'll need to make some SIMPLE changes.

 - .92 fixed bug that didn't include tag attributes

 (to use attributes, add _attributes[array_index]
 to the end of the tag in question:
 $xml_html_head_body_img would become
 $xml_html_head_body_img_attributes,
 for example)

 -- Thanks to Nick Winfield <nick@wirestation.co.uk>
 for reporting this bug.

 - .91 No Longer requires PHP4!

 - .91 now all elements are array. Using objects has
 been discontinued.
*/

class xml_container{

 function store($k,$v) {
 $this->{$k} = $v;
 }
}

/* parses the information */
/*********************************
* 类定义开始
*
*********************************/
class xml{

 // initialize some variables
 var $current_tag=array();
 var $xml_parser;
 var $Version = 1.0;
 var $tagtracker = array();

 /* Here are the XML functions needed by expat */

 /* when expat hits an opening tag, it fires up this function */
 function startElement($parser, $name, $attrs){

 array_push($this->current_tag, $name); // add tag to the cur. tag array
 $curtag = implode("_",$this->current_tag); // piece together tag

 /* this tracks what array index we are on for this tag */

 if(isset($this->tagtracker["$curtag"])) {
 $this->tagtracker["$curtag"]++;
 }
 else{
 $this->tagtracker["$curtag"]=0;
 }

 /* if there are attributes for this tag, we set them here. */

 if(count($attrs)>0) {
 $j = $this->tagtracker["$curtag"];
 if(!$j) $j = 0;

 if(!is_object($GLOBALS[$this->identifier]["$curtag"][$j])) {
 $GLOBALS[$this->identifier]["$curtag"][$j] = new xml_container;
 }

 $GLOBALS[$this->identifier]["$curtag"][$j]->store("attributes",$attrs);
 }

 }// end function startElement

 /* when expat hits a closing tag, it fires up this function */
 function endElement($parser, $name) {
 $curtag = implode("_",$this->current_tag); // piece together tag

 // before we pop it off,
 // so we can get the correct
 // cdata

 if(!$this->tagdata["$curtag"]) {
 $popped = array_pop($this->current_tag); // or else we screw up where we are
 return; // if we have no data for the tag
 }
 else{
 $TD = $this->tagdata["$curtag"];
 unset($this->tagdata["$curtag"]);
 }

 $popped = array_pop($this->current_tag);
 // we want the tag name for
 // the tag above this, it
 // allows us to group the
 // tags together in a more
 // intuitive way.

 if(sizeof($this->current_tag) == 0) return; // if we aren't in a tag

 $curtag = implode("_",$this->current_tag); // piece together tag
 // this time for the arrays

 $j = $this->tagtracker["$curtag"];

 if(!$j) $j = 0;

 if(!is_object($GLOBALS[$this->identifier]["$curtag"][$j])) {
 $GLOBALS[$this->identifier]["$curtag"][$j] = new xml_container;
 }

 $GLOBALS[$this->identifier]["$curtag"][$j]->store($name,$TD);
 #$this->tagdata["$curtag"]);
 unset($TD);
 return TRUE;
 } // end function endElement

 /* when expat finds some internal tag character data,
 it fires up this function */

 function characterData($parser, $cdata) {
 $curtag = implode("_",$this->current_tag); // piece together tag
 $this->tagdata["$curtag"] .= $cdata;
 }

 function xml($data,$identifier='xml') {

 $this->identifier = $identifier;

 // create parser object
 $this->xml_parser = xml_parser_create();

 // set up some options and handlers
 xml_set_object($this->xml_parser,$this);
 xml_parser_set_option($this->xml_parser,XML_OPTION_CASE_FOLDING,0);
 xml_set_element_handler($this->xml_parser, "startElement", "endElement");
 xml_set_character_data_handler($this->xml_parser, "characterData");

 if (!xml_parse($this->xml_parser, $data, TRUE)) {
 sprintf("XML error: %s at line %d",
 xml_error_string(xml_get_error_code($this->xml_parser)),
 xml_get_current_line_number($this->xml_parser));
 }

 // we are done with the parser, so let's free it
 xml_parser_free($this->xml_parser);

 }//end constructor: function xml()

}//thus, we end our class xml

?>

操作方法：

require('class.xml.php');
$file = "data.xml";
$data = implode("",file($file)) or die("could not open XML input file");
$obj = new xml($data,"xml");

print $xml["hans"]->num_results;
for($i=0;$i<sizeof($xml["hans"]);$i++) {
print $xml["hans"][$i]->tag . " ";
}

To print url attributes (if they exist):

print $xml["hans"]->attributes["size"];