PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

718 Chapter 30 Building a Mailing List Manager
Listing 30.12 subscribe()and unsubscribe() Functions from mlm_fns.php—
These Functions Add and Remove Subscriptions for a User
// subscribe this email address to this list
function subscribe($email, $listid) {
if((!$email) || (!$listid) || (!list_exists($listid))
|| (!subscriber_exists($email))) {
return false;
}
//if already subscribed exit
if(subscribed($email, $listid)) {
return false;
}
if(!($conn=db_connect())) {
return false;
}
$query = "insert into sub_lists values ('".$email."', $listid)";
$result = $conn->query($query);
return $result;
}
// unsubscribe this email address from this list
function unsubscribe($email, $listid) {
if ((!$email) || (!$listid)) {
return false;
}
if(!($conn=db_connect())) {
return false;
}
$query = "delete from sub_lists where email = '".$email."' and
listid = '".$listid."'";
$result = $conn->query($query);
return $result;
}
The subscribe() function adds a row to the sub_lists table corresponding to the
subscription; the unsubscribe() function deletes this row.