用正則表達式求出內容里面的以http://開頭的所有url地址

<?php
$str ='<a href="http://localhost">sina.com</a><a >健康網</a><a href="/aaa.html">sina.com</a>';
preg_match_all("/href=/"([^/"]+)/i", $str, $match);
$urls = $match[1];
$is_url = $_server['server_name'];
foreach($urls as $value)
{
    if(strstr($value, $is_url))  continue;
    echo $value . "<br />";
}
?>