用正则表达式求出内容里面的以http://开头的所有url地址

<?php
$str ='<a href="http://localhost">sina.com</a><a href="http://www.olders.net">健康网</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 />";
}
?>