Simple PHP Ban IP Address Script

// IP to ban
$banned_ip = "1.2.3.4";

// user's IP is held in the $_SERVER variable
$user_ip = $_SERVER['REMOTE_ADDR'];

// check if user's IP matches banned IP
if($user_ip == $banned_ip) {
    echo "Access denied";
}

// multiple IP addresses?
$banned_ips = array("1.2.3.4", "4.3.2.1");

// check for match
foreach($banned_ips as $ip_ban) {
    if($user_ip == $ip_ban) {
        echo "Access denied";
    }
}

?>