Fletcher-Checksums added

Following a user-request I added fletcher-checksums (8Bit-Fletcher and 16Bit-Fletcher) to http://serversniff.de/crypt-checksum.php.
I couldn't find any ready-to-use implementation, so recoded it in php. for the sake of having a fletcher-implementation in php online:

# 8 bit-fletcher
# codes an 8bit-fletcher-hash out of an
# hexencoded input-string
# consider this code public domain
#
$x="10111214" #hexecoded input-string
$twochunks=str_split($x,2); # split string into chunks
$lastleft=1; $lastright=0; # init
$modulo=65535; # fletcher-modulus
foreach($twochunks as $char)
{
$lastleft=fmod(($lastleft+hexdec($char)),$modulo); #left
$lastright=fmod(($lastright+$lastleft),$modulo); #right
}

$hexright=dechex($lastright); # make a hexval out of the old dec-val
$hexleft=dechex($lastleft); # make a hexval out of the old dec-val
$fletcher8="$hexright"."$hexleft"; # combine the two
print $fletcher8;
exit;