Hashing Algorithm usage

MD5 has been totally deprecated for usage when collisions may be an
issue - we should migrate to SHA-1 going forward.

SHA-1 isn't the best choice either - it's relatively performance hungry
since it is designed to be cryptographically secure.  Something like
Murmurhash3 would be much more desirable (and it is 128-bits).  But
SHA-1 is the best choice of the built-in PHP hash algorithms.

horde/docs/CODING_STANDARDS

@@ -869,3 +869,18 @@ fread() to get the stream data::
     while (!feof($stream)) {
         echo fread($stream, 8192);
     }
+
+
+Hashing Algorithm
+=================
+
+SHA-1
+-----
+SHA-1 is the recommended algorithm to use for non-cryptographic hashing
+actions::
+
+    $hash = hash('sha1', $string);
+
+MD5 should NOT be used, as it has known collision issues. (NOTE: SHA-1 hashes
+are 160-bit vs. MD5 hashes which are 128-bit; care needs to be taken if
+switching between methods regarding storage side of the hash string).