php解析字符串里所有URL地址的方法

<?php
// $html = the html on the page
// $current_url = the full url that the html came from
//(only needed for $repath)
// $repath = converts ../ and / and // urls to full valid urls
function pageLinks($html, $current_url = "", $repath = false){
preg_match_all("/<a.+?href=("|')(?!javascript:|#)(.+?)("|')/i", $html, $matches);
$links = array();
if(isset($matches[2])){
$links = $matches[2];
}
if($repath && count($links) > 0 && strlen($current_url) > 0){
$pathi = pathinfo($current_url);
$dir = $pathi["dirname"];
$base = parse_url($current_url);
$split_path = explode("/", $dir);
$url = "";
foreach($links as $k => $link){
if(preg_match("/^../", $link)){
$total = substr_count($link, "../");
for($i = 0; $i < $total; $i++){
array_pop($split_path);
}
$url = implode("/", $split_path) . "/" . str_replace("../", "", $link);
}elseif(preg_match("/^///", $link)){
$url = $base["scheme"] . ":" . $link;
}elseif(preg_match("/^/|^.//", $link)){
$url = $base["scheme"] . "://" . $base["host"] . $link;
}elseif(preg_match("/^[a-zA-Z0-9]/", $link)){
if(preg_match("/^http/", $link)){
$url = $link;
}else{
$url = $dir . "/" . $link;
}
}
$links[$k] = $url;
}
}
return $links;
}
header("content-type: text/plain");
$url = "http://www.jb51.net";
$html = file_get_contents($url);
// Gets links from the page:
print_r(pageLinks($html));
// Gets links from the page and formats them to a full valid url:
print_r(pageLinks($html, $url, true));