[loyo]

you'd better use cookie to do it.
example code

PHP Code:

<?php

//get their ip address
    if (getenv("HTTP_CLIENT_IP")) $ip = getenv("HTTP_CLIENT_IP");
    else if(getenv("HTTP_X_FORWARDED_FOR")) $ip = getenv("HTTP_X_FORWARDED_FOR");
    else if(getenv("REMOTE_ADDR")) $ip = getenv("REMOTE_ADDR");
    else $ip = "0.0.0.0";
$cvip = str_replace(".","_",$ip);
$timestamp = time();
if(empty($HTTP_COOKIE_VARS[$cvip])&&empty($_COOKIE[$cvip])){
    setcookie($cvip,$cvip,$timestamp+24*60*60);
    echo "welcome to our site, your ip is ".$ip;
}else
{
    echo "you have visited: ".$ip;
}
?>