1. 单向xml2array函数
Php代码 
function xml2array($contents, $get_attributes=1, $priority = 'tag')
{
if(!$contents) return array();
if(!function_exists('xml_parser_create')) {
//print "'xml_parser_create()' function not found!";
return array();
}
//Get the XML parser of PHP - PHP must have this module for the parser to work
$parser = xml_parser_create('');
xml_parser_set_option($parser, XML_OPTION_TARGET_ENCODING, "UTF-8"); # http://minutillo.com/steve/weblog/2004/6/17/php-xml-and-character-encodings-a-tale-of-sadness-rage-and-data-loss
xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, 0);
xml_parser_set_option($parser, XML_OPTION_SKIP_WHITE, 1);
xml_parse_into_struct($parser, trim($contents), $xml_values);
xml_parser_free($parser);
if(!$xml_values) return;//Hmm...
//Initializations
$xml_array = array();
$parents = array();
$opened_tags = array();
$arr = array();
$current = &$xml_array; //Refference
//Go through the tags.
$repeated_tag_index = array();//Multiple tags with same name will be turned into an array
foreach($xml_values as $data) {
unset($attributes,$value);//Remove existing values, or there will be trouble
//This command will extract these variables into the foreach scope
// tag(string), type(string), level(int), attributes(array).
extract($data);//We could use the array by itself, but this cooler.
$result = array();
$attributes_data = array();
if(isset($value)) {
if($priority == 'tag') $result = $value;
else $result['value'] = $value; //Put the value in a assoc array if we are in the 'Attribute' mode
}
//Set the attributes too.
if(isset($attributes) and $get_attributes) {
foreach($attributes as $attr => $val) {
if($priority == 'tag') $attributes_data[$attr] = $val;
else $result['attr'][$attr] = $val; //Set all the attributes in a array called 'attr'
}
}
//See tag status and do the needed.
if($type == "open") {//The starting of the tag '<tag>'
$parent[$level-1] = &$current;
if(!is_array($current) or (!in_array($tag, array_keys($current)))) { //Insert New tag
$current[$tag] = $result;
if($attributes_data) $current[$tag. '_attr'] = $attributes_data;
$repeated_tag_index[$tag.'_'.$level] = 1;
$current = &$current[$tag];
} else { //There was another element with the same tag name
if(isset($current[$tag][0])) {//If there is a 0th element it is already an array
$current[$tag][$repeated_tag_index[$tag.'_'.$level]] = $result;
$repeated_tag_index[$tag.'_'.$level]++;
} else {//This section will make the value an array if multiple tags with the same name appear together
$current[$tag] = array($current[$tag],$result);//This will combine the existing item and the new item together to make an array
$repeated_tag_index[$tag.'_'.$level] = 2;
if(isset($current[$tag.'_attr'])) { //The attribute of the last(0th) tag must be moved as well
$current[$tag]['0_attr'] = $current[$tag.'_attr'];
unset($current[$tag.'_attr']);
}
}
$last_item_index = $repeated_tag_index[$tag.'_'.$level]-1;
$current = &$current[$tag][$last_item_index];
}
} elseif($type == "complete") { //Tags that ends in 1 line '<tag />'
//See if the key is already taken.
if(!isset($current[$tag])) { //New Key
$current[$tag] = $result;
$repeated_tag_index[$tag.'_'.$level] = 1;
if($priority == 'tag' and $attributes_data) $current[$tag. '_attr'] = $attributes_data;
} else { //If taken, put all things inside a list(array)
if(isset($current[$tag][0]) and is_array($current[$tag])) {//If it is already an array...
// ...push the new element into that array.
$current[$tag][$repeated_tag_index[$tag.'_'.$level]] = $result;
if($priority == 'tag' and $get_attributes and $attributes_data) {
$current[$tag][$repeated_tag_index[$tag.'_'.$level] . '_attr'] = $attributes_data;
}
$repeated_tag_index[$tag.'_'.$level]++;
} else { //If it is not an array...
$current[$tag] = array($current[$tag],$result); //...Make it an array using using the existing value and the new value
$repeated_tag_index[$tag.'_'.$level] = 1;
if($priority == 'tag' and $get_attributes) {
if(isset($current[$tag.'_attr'])) { //The attribute of the last(0th) tag must be moved as well
$current[$tag]['0_attr'] = $current[$tag.'_attr'];
unset($current[$tag.'_attr']);
}
if($attributes_data) {
$current[$tag][$repeated_tag_index[$tag.'_'.$level] . '_attr'] = $attributes_data;
}
}
$repeated_tag_index[$tag.'_'.$level]++; //0 and 1 index is already taken
}
}
} elseif($type == 'close') { //End of tag '</tag>'
$current = &$parent[$level-1];
}
}
return($xml_array);
}
$priority设置为空的时候，可以获取所有节点属性值。
优点： 获取的节点属性不占用数组父级键。
缺点： $priority设置为tag时，获取节点属性值不太理想。
2. 双向xml2array和array2xml函数
Php代码
<?php
###################################################################################
# xml2array: takes raw XML as a parameter (a string)
# and returns an equivalent PHP data structure
###################################################################################
function & xml2array(&$xml,$attr=true){
$xml_parser = &new XML();
$xml_parser->attr = $attr;
$data = &$xml_parser->parse($xml);
$xml_parser->destruct();
return $data;
}
###################################################################################
# array2xml: serializes any PHP data structure into XML
# Takes one parameter: the data to serialize. Must be an array.
###################################################################################
function & array2xml(&$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($key, '_attr')) #if it's not an attribute
#we don't treat attributes by themselves, so for an emptyempty element
# that has attributes you still need to set the element to NULL
if(is_array($value) and array_key_exists(0, $value)){
array2xml($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),"</$tag>\n";
else echo ">\n",array2xml($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.
var $attr = true;
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 = $tag;
#if you've seen this tag before
if(is_array($this->parent) and array_key_exists($tag,$this->parent))
{
#if the keys are numeric
#this is the third or later instance of $tag we've come across
if(is_array($this->parent[$tag]) and array_key_exists(0,$this->parent[$tag])) $key = $this->count_numeric_items($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 AND $this->attr) $this->parent[$key.'_attr'] = $attributes;
$this->parent = &$this->parent[$key];
$this->stack[] = &$this->parent;
}
function data(&$parser, $data)
{
#you don't need to store whitespace in between tags
if($this->last_opened_tag != NULL) $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;
}
}
实例：
Php代码
<?php
include('xml.php');
$data = xml2array($xml);
?>
Php代码
<?php
include('xml.php');
$xml = array2xml($data);
?>
来源： http://keithdevens.com/software/phpxml
该类已根据来源代码做了修改。
如果$attr设置为false，输出的数组中将不包括节点属性值。
优点： 获取节点属性值较理想。
缺点： 获取的节点属性占用数组父级键