PHP Session Identifiers using SHA256 algorithm don't allow successful login

[Alex Harrington]

2012-03-12 11:44:25
The query [INSERT INTO session (session_id, session_data, session_expiration, LastAccessed, LastPage, userID, IsExpired, UserAgent, RemoteAddr)
     VALUES ('g77fq7qup6vr7r3btf5c1p71e061o8lbsj799h4govsuf79khkn0', 'pagename|s:5:\"index\";token|s:32:\"1a2164a28265546500a2213a557b68e2\";token_timeout|i:1331552665;', 1331554105, '2012-03-12 11:44:25', 'login', NULL, 0, 'Mozilla/5.0 (X11; Linux x86_64; rv:10.0.2) Gecko/20100101 Firefox/10.0.2', 'xx')] failed to execute<br />MySQL error: Duplicate entry 'g77fq7qup6vr7r3btf5c1p71e061o8lb' for key 'PRIMARY'

The php.ini differs for the 2 installations. Here what I had to change in it:
; Select a hash function for use in generating session ids.
; Possible Values
; 0 (MD5 128 bits)
; 1 (SHA-1 160 bits)
; This option may also be set to the name of any hash function supported by
; the hash extension. A list of available hashes is returned by the hash_algos()
; function.
; http://php.net/session.hash-function
;session.hash_function = sha256
session.hash_function = 3

I commented out the sha256 and added the value 3 as it was in the older versions. That's all. That's the little devil who did all this work to me.