php/ gethostbyname() IP取得 ドメインを取得する


   $subdomain = preg_replace("/https?:\/\//iu", "", $row["url"]);
    if(
    $tmp = preg_split("/\//u", $subdomain)
    ){
        $subdomain = $tmp[0];
    } else{
        $subdomain = $row["url"];
    }
//print_r($tmp);
    $ip = "";
    if(
    preg_match("/([-a-z0-9]+\\.[a-z]+)$/iu", $subdomain, $match)
    ){
        $ip = gethostbyname($match[1]);
    }
    if(
    preg_match("/^[0-9.]+$/u", $ip)
    ){
        $subdomain = $match[1];
    } elseif(
    preg_match("/([-a-z0-9]+\\.[a-z]+\\.[a-z]+)$/iu", $subdomain, $match)
    ){
        $ip = gethostbyname($match[1]);
        if(
        preg_match("/^[0-9.]+$/u", $ip)
        ){
            $subdomain = $match[1];
        }
    }

( Thanks. )
gethostbyname
http://www.php.net/manual/ja/function.gethostbyname.php