referencing a variable which is a string by the $this within a string doesn't work.

$qry = "UPDATE visits SET timeout=Now(), WHERE sessionid='$this->$sid'";

if i do this, it works:

$sid = $this->$sid;
$qry = "UPDATE visits SET timeout=Now(), WHERE sessionid='$sid'";

the parser error is:

Parse error: parse error, expecting `STRING' in includes/functions.inc on line 89

$sid is declared at the top of the class as:

var $sid="";