Welcome to PHP please use the boards [NOPARSE]
[/NOPARSE] when posting php code to make it easier to read and analyze. As for your problem:
if ($update == "yes"){
$update = "update A06_ProBill_Items_T set A06_Comments='$A06_Comments' where A06_DRS_Freight_Id='$freightid'";
}
You define an update variable but you never execute the query so of course the "query" isn't producing the results you want, because you never run it.