How to clean up extended charset or ASCII characters on form input?

["Eric Wood" <eric@xxxxxxxxxxxxx>]

I've searched of 21000 messages in this list and I don't quite understand how to best protect user input.

Let's say you have a form that posts to itself just do see how messed up data can get:

>>>>>>>>>>>>>>>>>>>>>>
if(get_magic_quotes_gpc()) {
   $_POST=array_map('stripslashes',$_POST);
}
$_POST=array_map('trim',$_POST);
$fname=$_POST["fname"];
<input name="fname" value="<? echo htmlentities($fname); ?>">
<<<<<<<<<<<<<<<<<<<<<<

htmlentities() does a good job to protecting quotes and allows for pretty flexible data entry characters.

I found another function on the internet called "cleanconvertaccents" which I can run through array_map.  However it's not perfect.

If you enter an ALT-151 charcter, the value of the input keeps getting longer and longer as it double encodes on each submission.

newegg.com does a good job to maintaining extended characters (presenting them back to the user) and keeps them from getting out of hand.

How do other do this?

thanks,
-Eric Wood