php使用正则表达式解析字符串里的所有URL地址

<?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://phpsnips.com"; 
$html = file_get_contents($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));