Can someone give me a good Ban IP script?

Can someone give me a good ban ip script? Something like you have to put it in the head section of the page and then the people from the ip you filled in can't see the page? Please help me.
Cheers MPCODER

Banning doesn't always work correctly and you can sometimes ban people you don't mean to ban, but here you go.

<?
$ip = $_SERVER['REMOTE_ADDR'];
$bannedips = array("IP HERE","IP HERE","IP HERE");
if (in_array($ip, $bannedips)) {

// disallow

} else {

// allow

}
?>

Thank you!:)