PHP, crawler PHP implements the simplest crawler prototype

<?php
/**
 * 爬虫程序 -- 原型
 * 
 * BookMoth 2009-02-21
 */
/**
 * 从给定的url获取html内容
 *
 * @param string $url
 * @return string
 */
function _getUrlContent($url){
$handle = fopen($url, "r");
if($handle){
$content = stream_get_contents($handle,1024*1024);
return $content;
}else{
return false;
}
}
/**
 * 从html内容中筛选链接
 *
 * @param string $web_content
 * @return array
 */
function _filterUrl($web_content){
$reg_tag_a = &#39;/<[a|A].*?href=[/&#39;/"]{0,1}([^>/&#39;/"/ ]*).*?>/&#39;;
$result = preg_match_all($reg_tag_a,$web_content,$match_result);
if($result){
return $match_result[1];
}
}
/**
 * 修正相对路径
 *
 * @param string $base_url
 * @param array $url_list
 * @return array
 */
function _reviseUrl($base_url,$url_list){
$url_info = parse_url($base_url);
$base_url = $url_info["scheme"].&#39;://&#39;;
if($url_info["user"]&&$url_info["pass"]){
$base_url .= $url_info["user"].":".$url_info["pass"]."@";
}
$base_url .= $url_info["host"];
if($url_info["port"]){
$base_url .= ":".$url_info["port"];
}
$base_url .= $url_info["path"];
print_r($base_url);
if(is_array($url_list)){
foreach ($url_list as $url_item) {
if(preg_match(&#39;/^http/&#39;,$url_item)){
//已经是完整的url
$result[] = $url_item;
}else {
//不完整的url
$real_url = $base_url.&#39;/&#39;.$url_item;
$result[] = $real_url;
}
}
return $result;
}else {
return;
}
}
/**
 * 爬虫
 *
 * @param string $url
 * @return array
 */
function crawler($url){
$content = _getUrlContent($url);
if($content){
$url_list = _reviseUrl($url,_filterUrl($content));
if($url_list){
return $url_list;
}else {
return ;
}
}else{
return ;
}
}
/**
 * 测试用主程序
 *
 */
function main(){
$current_url = "http://hao123.com/";//初始url
$fp_puts = fopen("url.txt","ab");//记录url列表
$fp_gets = fopen("url.txt","r");//保存url列表
do{
$result_url_arr = crawler($current_url);
if($result_url_arr){
foreach ($result_url_arr as $url) {
fputs($fp_puts,$url."/r/n");
}
}
}while ($current_url = fgets($fp_gets,1024));//不断获得url
}
main();
?>