I get the following error when running the E-Commerce example from code downloaded from Wrox site:

Warning: Wrong parameter count for mysql_query() in c:\Apache Group\Apache2\htdocs\checkout2.php on line 244

Line 244 is the "or die " line in the following command sequence:
$query = "SELECT * FROM carttemp WHERE" .
         "carttemp_sess = ". $sessid;
$results = mysql_query($query)
    or die(mysql_query());

It looks to me like the $query is wrong:

$query = "SELECT * FROM carttemp WHERE" .
         "carttemp_sess = ". $sessid;

needs to be:

$query = "SELECT * FROM carttemp WHERE carttemp_sess='$sessid'";

Hope that helps