Sessions fail when generated IDs are greater than 32 characters.

[zerocrates]

See http://omeka.org/forums/topic/admin-login-screen-seems-to-redirect-on-itself

The default PHP session ID is 32 characters long, a hexadecimal representation of a 128-bit MD5 hash. Users can set session.hash_function to '1', which uses SHA-1 instead, and produces 160-bit (40 hex character) hashes. Users can also pick even bigger hashes like sha256 and sha512.

The table we use to store sessions stores the ID (the primary key) as a CHAR(32), so we're truncating any longer ids. This means they won't get looked up correctly, and sessions just won't work. For the SHA-1 setting, users can work around this problem by also setting session.hash_bits_per_character to 5.

We need to do some combination of forcing the hash function PHP uses and altering the sessions table to accommodate bigger session ids.

[jimsafley]

Is this as easy as altering sessions.id from CHAR(32) to VARCHAR(128)?