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　　今天在PHP4环境下重新写一个接口程序，需要大量分析解析XML，PHP的xml_parse_into_struct()函数不能直接生成便于使用的数组，而SimpleXML扩展在PHP5中才支持，于是逛逛搜索引擎，在老外的网站上找到了一个不错的PHP XML操作类。

一、用法举例：
1、将XML文件解释成便于使用的数组：
<?php include('xml.php');    //引用PHP XML操作类 $xml = file_get_contents('data.xml');    //读取XML文件 //$xml = file_get_contents("php://input");    //读取POST过来的输入流 $data=XML_unserialize($xml); echo '<pre>'; print_r($data); echo '</pre>'; ?>

data.xml文件：
<?xml version="1.0" encoding="GBK"?> <video> <upload> <videoid>998</videoid> <name><![CDATA[回忆未来]]></name> <memo><![CDATA[def]]></memo> <up_userid>11317</up_userid> </upload> </video>

利用该XML操作类生成的对应数组（汉字编码：UTF-8）：
Array (    [video] => Array        (            [upload] => Array                (                    [videoid] => 998                    [name] => 回忆未来                    [memo] => def                    [up_userid] => 11317                )        ) )

2、将数组转换成XML文件：
<?php include('xml.php');//引用PHP XML操作类 $xml = XML_serialize($data); ?>

二、PHP XML操作类源代码：
<?php ################################################################################### # # XML Library, by Keith Devens, version 1.2b # <a href="http://keithdevens.com/software/phpxml" target="_blank">http://keithdevens.com/software/phpxml</a> # # This code is Open Source, released under terms similar to the Artistic License. # Read the license at <a href="http://keithdevens.com/software/license" target="_blank">http://keithdevens.com/software/license</a> # ################################################################################### ################################################################################### # XML_unserialize: takes raw XML as a parameter (a string) # and returns an equivalent PHP data structure ################################################################################### function & XML_unserialize(&$xml){    $xml_parser = &new XML();    $data = &$xml_parser->parse($xml);    $xml_parser->destruct();    return $data; } ################################################################################### # XML_serialize: serializes any PHP data structure into XML # Takes one parameter: the data to serialize. Must be an array. ################################################################################### function & XML_serialize(&$data, $level = 0, $prior_key = NULL){    if($level == 0){ ob_start(); echo '<?xml version="1.0" ?>',"\n"; }    while(list($key, $value) = each($data))        if(!strpos($key, ' attr')) #if it's not an attribute            #we don't treat attributes by themselves, so for an empty element            # that has attributes you still need to set the element to NULL            if(is_array($value) and array_key_exists(0, $value)){                XML_serialize($value, $level, $key);            }else{                $tag = $prior_key ? $prior_key : $key;                echo str_repeat("\t", $level),'<',$tag;                if(array_key_exists("$key attr", $data)){ #if there's an attribute for this element                    while(list($attr_name, $attr_value) = each($data["$key attr"]))                        echo ' ',$attr_name,'="',htmlspecialchars($attr_value),'"';                    reset($data["$key attr"]);                }                if(is_null($value)) echo " />\n";                elseif(!is_array($value)) echo '>',htmlspecialchars($value),"</$tag>\n";                else echo ">\n",XML_serialize($value, $level+1),str_repeat("\t", $level),"</$tag>\n";            }    reset($data);    if($level == 0){ $str = &ob_get_contents(); ob_end_clean(); return $str; } } ################################################################################### # XML class: utility class to be used with PHP's XML handling functions ################################################################################### class XML{    var $parser;   #a reference to the XML parser    var $document; #the entire XML structure built up so far    var $parent;   #a pointer to the current parent - the parent will be an array    var $stack;    #a stack of the most recent parent at each nesting level    var $last_opened_tag; #keeps track of the last tag opened.    function XML(){         $this->parser = &xml_parser_create();        xml_parser_set_option(&$this->parser, XML_OPTION_CASE_FOLDING, false);        xml_set_object(&$this->parser, &$this);        xml_set_element_handler(&$this->parser, 'open','close');        xml_set_character_data_handler(&$this->parser, 'data');    }    function destruct(){ xml_parser_free(&$this->parser); }    function & parse(&$data){        $this->document = array();        $this->stack    = array();        $this->parent   = &$this->document;        return xml_parse(&$this->parser, &$data, true) ? $this->document : NULL;    }    function open(&$parser, $tag, $attributes){        $this->data = ''; #stores temporary cdata        $this->last_opened_tag = $tag;        if(is_array($this->parent) and array_key_exists($tag,$this->parent)){ #if you've seen this tag before            if(is_array($this->parent[$tag]) and array_key_exists(0,$this->parent[$tag])){ #if the keys are numeric                #this is the third or later instance of $tag we've come across                $key = count_numeric_items($this->parent[$tag]);            }else{                #this is the second instance of $tag that we've seen. shift around                if(array_key_exists("$tag attr",$this->parent)){                    $arr = array('0 attr'=>&$this->parent["$tag attr"], &$this->parent[$tag]);                    unset($this->parent["$tag attr"]);                }else{                    $arr = array(&$this->parent[$tag]);                }                $this->parent[$tag] = &$arr;                $key = 1;            }            $this->parent = &$this->parent[$tag];        }else{            $key = $tag;        }        if($attributes) $this->parent["$key attr"] = $attributes;        $this->parent  = &$this->parent[$key];        $this->stack[] = &$this->parent;    }    function data(&$parser, $data){        if($this->last_opened_tag != NULL) #you don't need to store whitespace in between tags            $this->data .= $data;    }    function close(&$parser, $tag){        if($this->last_opened_tag == $tag){            $this->parent = $this->data;            $this->last_opened_tag = NULL;        }        array_pop($this->stack);        if($this->stack) $this->parent = &$this->stack[count($this->stack)-1];    } } function count_numeric_items(&$array){    return is_array($array) ? count(array_filter(array_keys($array), 'is_numeric')) : 0; } ?>