Why does MySQL ENCRYPT() give the same value?

Question

Part of the code I'm using is:

        $password = MD5($password);

        $account_created = date("Y-m-d H-i-s");

        db_insert("users","user_id,username,password,account_created,registration_ip","ENCRYPT('$_POST[username] $account_created'),'$_POST[username]',MD5('$_POST[password]'),'$account_created','$_SERVER[REMOTE_ADDR]'");

        $user = db_get_array("users","username='$_POST[username]'");

        db_insert("usersettings","user_id,timezone","'$user[user_id]','$_POST[timezone]'");

        db_update("users","login_id = ENCRYPT('$user[username] $password')","user_id='$user[user_id]'");

The script continues before and after that

Anyway, the problem I'm having is that, there are two calls to ENCRYPT() in the MySQL queries, but for some reason both of them have the same values

The user ID and login ID are meant to be different, whats the problem?

Answer 1

ENCRYPT() ignores all but the first eight characters of str, at least on some systems. This behavior is determined by the implementation of the underlying crypt() system call.

http://dev.mysql.com/doc/refman/5.1/en/encryption-functions.html#function_encrypt

So if your username is longer than 8 characters...