PHP and MySQL Web Development - P136 potx

647
Implementing User Functions
Now that we know how this list is produced, let’s look at the action buttons associat-
ed with these displays.
Viewing List Information
The Information button shown in Figure 28.7 triggers the 'information' action,
which is as follows:
case 'information' :
{
display_information($HTTP_GET_VARS['id']);
break;
}
To see what the display_information() function does, look at Figure 28.8.
Figure 28.8 The display_information() function
shows a blurb about a mailing list.
The function displays some general information about a particular mailing list, as well as
listing the number of subscribers and the number of newsletters that have been sent out
to that list and are available in the archive (more on that in a minute).
The code for this function is shown in Listing 28.9.
34 525x ch28 1/24/03 2:55 PM Page 647
648
Chapter 28 Building a Mailing List Manager
Listing 28.9 display_information() Function from output_fns.php—Displaying List
Information
function display_information($listid)
{
if(!$listid)
return false;
$info = load_list_info($listid);
if($info)
{

echo '<h2>'.pretty($info[listname]).'</h2>';
echo '<p>'.pretty($info[blurb])'</p>;
echo '<p>Number of subscribers:' . $info[subscribers]'</p>;
echo '<p>Number of messages in archive:' . $info[archive]'</p>;
}
}
The display_information() function uses two other functions to help it achieve its
Web task: the load_list_info() function and the pretty() function.The
load_list_info() function actually retrieves the data from the database.The
pretty() function simply formats the data from the database by stripping out slashes,
turning newlines into HTML line breaks, and so on.
Let’s look briefly at the load_list_info() function.This function is in the
mlm_fns.php function library.The code for it is shown in Listing 28.10.
Listing 28.10 load_list_info() Function from mlm_fns.php—Building an Array of List
Information
function load_list_info($listid)
{
if(!$listid)
return false;
if(!db_connect())
return false;
$query = "select listname, blurb from lists where listid = $listid";
$result = mysql_query($query);
if(!$result)
{
echo 'Cannot retrieve this list';
return false;
}
$info = mysql_fetch_array($result);
34 525x ch28 1/24/03 2:55 PM Page 648

649
Implementing User Functions
$query = "select count(*) from sub_lists where listid = $listid";
$result = mysql_query($query);
if($result)
{
$info['subscribers'] = mysql_result($result, 0, 0);
}
$query = "select count(*) from mail where listid = $listid
and status = 'SENT'";
$result = mysql_query($query);
if($result)
{
$info['archive'] = mysql_result($result, 0, 0);
}
return $info;
}
This function runs three database queries to collect the name and blurb for a list from
the lists table, the number of subscribers from the sub_lists table, and the number of
newsletters sent from the mail table.
Viewing List Archives
In addition to viewing the list blurb, users can look at all the mail that has been sent to a
mailing list by clicking on the Show Archive button.This activates the show-archive
action, which triggers the following code:
case 'show-archive' :
{
display_items('Archive For '.get_list_name($HTTP_GET_VARS['id']),
get_archive($HTTP_GET_VARS['id']), 'view-html', 'view-text', '');
break;
}

Again, this function uses the display_items() function to list out the various items of
mail that have been sent to the list.These items are retrieved using the
get_archive()
function from mlm_fns.php.This function is shown in Listing 28.11.
Listing 28.11 get_archive() Function from mlm_fns.php—Building an Array of
Archived Newsletters for a Given List
function get_archive($listid)
{
//returns an array of the archived mail for this list
//array has rows like (mailid, subject)
$list = array();
Listing 28.10 Continued
34 525x ch28 1/24/03 2:55 PM Page 649
650
Chapter 28 Building a Mailing List Manager
$listname = get_list_name($listid);
$query = "select mailid, subject, listid from mail
where listid = $listid and status = 'SENT' order by sent";
if(db_connect())
{
$result = mysql_query($query);
if(!$result)
{
echo "<p>Unable to get list from database - $query.</p>";
return false;
}
$num = mysql_numrows($result);
for($i = 0; $i<$num; $i++)
{
$row = array(mysql_result($result, $i, 0),

mysql_result($result, $i, 1), $listname, $listid);
array_push($list, $row);
}
}
return $list;
}
Again, this function gets the required information—in this case, the details of mail that
has been sent—from the database and builds an array suitable for passing to the
display_items() function.
Subscribing and Unsubscribing
On the list of mailing lists shown in Figure 28.7, each list has a button that enables users
to subscribe to it. Similarly, if users use the Show My Lists option to see the lists to
which they are already subscribed, they will see an Unsubscribe button next to each list.
These buttons activate the subscribe and unsubscribe actions, which trigger the fol-
lowing two pieces of code, respectively:
case 'subscribe' :
{
subscribe(get_email(), $HTTP_GET_VARS['id']);
display_items('Subscribed Lists', get_subscribed_lists(get_email()),
'information', 'show-archive', 'unsubscribe');
break;
}
case 'unsubscribe' :
{
Listing 28.11 Continued
34 525x ch28 1/24/03 2:55 PM Page 650
651
Implementing User Functions
unsubscribe(get_email(), $HTTP_GET_VARS['id']);
display_items('Subscribed Lists', get_subscribed_lists(get_email()),

'information', 'show-archive', 'unsubscribe');
break;
}
In each case, we call a function (subscribe() or unsubscribe()) and then redisplay a
list of mailing lists the user is now subscribed to using the display_items() function
again.
The subscribe() and unsubscribe() functions are shown in Listing 28.12.
Listing 28.12 subscribe() and unsubscribe() Functions from mlm_fns.php—These
Functions Add and Remove Subscriptions for a User
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(!db_connect())
return false;
$query = "insert into sub_lists values ('$email', $listid)";
$result = mysql_query($query);
return $result;
}
function unsubscribe($email, $listid)
{
if(!$email||!$listid)
return false;
if(!db_connect())
return false;
$query = "delete from sub_lists where email = '$email' and listid = $listid";
$result = mysql_query($query);

return $result;
}
34 525x ch28 1/24/03 2:55 PM Page 651