PHP用SAX解析XML的实现代码与问题分析

<?php
$g_books = array();
$g_elem = null;
function startelement( $parser, $name, $attrs )
{
global $g_books, $g_elem;
if ( $name == 'book' ) $g_books []= array();
$g_elem = $name;
}
function endelement( $parser, $name )
{
global $g_elem;
$g_elem = null;
}
function textdata( $parser, $text )
{
global $g_books, $g_elem;
if ( $g_elem == 'author' ||
$g_elem == 'publisher' ||
$g_elem == 'title' )
{
$g_books[ count( $g_books ) - 1 ][ $g_elem ] = $text;
}
}
$parser = xml_parser_create();
xml_set_element_handler( $parser, "startelement", "endelement" );
xml_set_character_data_handler( $parser, "textdata" );
$f = fopen( 'books.xml', 'r' );
while( $data = fread( $f, 4096 ) )
{
xml_parse( $parser, $data );
}
xml_parser_free( $parser );
foreach( $g_books as $book )
{
echo $book['title']." - ".$book['author']." - ";
echo $book['publisher']."\n";
}
?>

<?xml version="1.0" encoding="gbk"?>
<result>
<row>
<id>1047869</id>
<date>2008-08-28 14:54:51</date>
<title>红花还需绿叶扶--浅谈脚架云台的选购</title>
<summary>很多专业摄影师在选购三脚架的时候，往往出手阔绰，3、4000元一个的捷信或者曼富图三脚架常常不用经过思考就买下来了，可是，他们却总是忽视了云台的精挑细眩其实，数码相机架在三脚架上面究竟稳不稳，起决定作用的是云台，那么我们如何才能挑选到一款稳如磐石的云台呢？云台家族种类繁多用途迥异简单的说，脚架云台是用于连接相机与脚架进行角度调节的部件，主要分成三维云台和球型云台。三维云台在横向旋转</summary>
</row>
...(省略若干行)
</result>

<?php
class xml {
var $parser;
var $i =0;
var $search_result = array();
var $row = array();
var $data = array();
var $now_tag;
var $tags = array("id", "classid", "subclassid", "classname", "title", "shorttitle", "author", "producer", "summary", "content", "date");
function xml()
{
$this->parser = xml_parser_create();
xml_set_object($this->parser, $this);
xml_set_element_handler($this->parser, "tag_open", "tag_close");
xml_set_character_data_handler($this->parser, "cdata");
}
function parse($data)
{
xml_parse($this->parser, $data);
}
function tag_open($parser, $tag, $attributes)
{
$this->now_tag=$tag;
if($tag=='result') {
$this->search_result = $attributes;
}
if($tag=='row') {
$this->row[$this->i] = $attributes;
}
}
function cdata($parser, $cdata)
{
if(in_array($this->now_tag, $this->tags)){
$tagname = strtolower($this->now_tag);
$this->data[$this->i][$tagname] = $cdata;
}
}
function tag_close($parser, $tag)
{
$this->now_tag="";
if($tag=='row') {
$this->i++;
}
}
}
?>

<?php
require_once("./xml_class.php");
$xml = file_get_contents("./so.xml");
$xml_parser = new xml();
$xml_parser->parse($xml);
print_r($xml_parser);
?>