OK. Cookie values should be available from the $_COOKIE superglobal array. So, let's say we have a cookie named "user" with the value "Fred".
We can concatenate variables with the '.' (that's a dot, or period, or actually the concatenation operator).
So, you have an item coming from a POSTed form. Maybe it's a beanshooter....
$Value4DB=$_POST['item']."=".$COOKIE['user'];
This variable should read, in this case,
beanshooter=fred
HTH,