https://github.com/mikewest/http-state-tokens

I defined this on a client site with thoughts about using it in the future...

$GLOBALS['SITE_DB']->create_table('session_data', array(
's_session_id' => '*ID_TEXT',
's_key' => '*ID_TEXT',
's_val' => 'LONG_TEXT',
));

function get_session_val($key)
{
return $GLOBALS['SITE_DB']->query_select_value_if_there('session_data', 's_val', array(
's_session_id' => get_session_id(true),
's_key' => $key,
));
}

function set_session_val($key, $val)
{
$GLOBALS['SITE_DB']->query_delete('session_data', array(
's_session_id' => get_session_id(true),
's_key' => $key,
));
if ($val !== null) {
$GLOBALS['SITE_DB']->query_insert('session_data', array(
's_session_id' => get_session_id(true),
's_key' => $key,
's_val' => $val,
));
}
}

The query_delete/query_insert combo could be replaced with query_insert_or_replace in v11+.

Be careful...

Implementation needs to consider cases where a user might actually want these values to be cleared (e.g. they clear their browser cookies).