Finally had time to sit down and implement this and wanted to both receive criticism for my code and to allow others to use it if they wish.
The code turned out to be extremely simple and works directly with the string representation itself so there is no decode/re-encode necessary
function reverseHash($hash){
$ret = "";
for($i = 0; $i<63; $i+=2){
$ret .= $hash[62-$i].$hash[63-$i];
}
return $ret;
}