In trying to get the ssi_login aspect of SMF to work within Modx, it would seem that the login link generated by SMF uses a session called rand_code, which comes from the sessions table in the SMF database. When the login link is placed within a Modx page it seems to get a different value for rand_code.
Can someone confirm where Modx would store a session variable called rand_code, if indeed there is one. I am assuming that Modx must be doing something using rand_code?
<EDIT>
Got it working
Had this nagging doubt about the SSI.php include being in the snippet, so I removed it from the snippet and simply placed the includes such as sss_welcome() in the snippet. I then placed the SSI.php include right at the beginning of the Modx index.php. The ssi_login and ssi_logout now have the correct sessions and work as they should from Modx pages.