Skal gemme teksten som UTF-8

Jeg har brug for at dette PHP-script gemmer teksten som UTF-8, men ved ikke hvordan .....

Kan nogen hjælpe??

<?
        $Website = eregi_replace("http://", "", $Website);
        $Name = stripslashes($Name);
        $Country  = stripslashes($Country);
        $Email = stripslashes($Email);
        $Website = stripslashes($Website);
        $Comments = stripslashes($Comments);
if ($Submit == "Yes") {
        $filename = "GuestBog_37.txt";
        $fp = fopen( $filename,"r");
        $OldData = fread($fp, 80000);
        fclose( $fp );
        $Today = (date ("l dS of F Y ( h:i:s A )",time()));
        $Input = "Name: <b>$Name</b><br>Country: <b>$Country</b><br>Email: <b><u><a href=\"mailto:$Email\">$Email</a></b></u><br>Website: <b><u><a href=\"http://$Website\" target=\"_blank\">$Website</a></b></u><br>Comments: <b>$Comments</b><br>Date: $Today<br><br>**************************************<br><br>.:::.";
  $New = "$Input$OldData";
        $fp = fopen( $filename,"w+");
        fwrite($fp, $New, 80000);
        fclose( $fp );
}
        $filename = "GuestBook.txt";
        $fp = fopen( $filename,"r");
        $Data = fread($fp, 80000);
        fclose( $fp );
        $DataArray = split (".:::.", $Data);
        $NumEntries = count($DataArray) - 1;
        print "&TotalEntries=$NumEntries&NumLow=$NumLow&NumHigh=$NumHigh&GuestBook=";
        for ($n = $NumLow; $n < $NumHigh; $n++) {
        print $DataArray[$n];
                if (!$DataArray[$n]) {
                Print "<br><b>No More entries</b>";
                exit;
                }
        }
?>