经测试代码如下：
/**
* 相对路径转化成绝对路径
*
* @param
* @author 编程之家 jb51.cc jb51.cc
**/
function relative_to_absolute($content,$Feed_url) {
preg_match('/(http|https|ftp):///',$Feed_url,$protocol);
$server_url = preg_replace("/(http|https|ftp|news):///","",$Feed_url);
$server_url = preg_replace("//.*/",$server_url);
if ($server_url == '') {
return $content;
}
if (isset($protocol[0])) {
$new_content = preg_replace('/href="//','href="'.$protocol[0].$server_url.'/',$content);
$new_content = preg_replace('/src="//','src="'.$protocol[0].$server_url.'/',$new_content);
} else {
$new_content = $content;
}
return $new_content;
}
/*** 来自编程之家 jb51.cc（jb51.cc） ***/