Variable tracking for PHPInvoicer

SESSION VARIABLES:

first setup:
$_SESSION[fieldname];
$_SESSION[errornum];

once logged in.
$_SESSION[username] is the username.
$_SESSION[admin] 1 or 0.
$_SESSION[loggedin] 1 or 0 for valid system user.
$_SESSION[loggedinuserid] for which user is logged in.