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Creating an Online Storefront in PHP, MySQL and Apache, Part 2

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In Part 2 of this chapter, you’ll learn the design process behind a simple discussion forum; specifically, displaying the topic list.

Read part 1 of this chapter series. If you're interested in seeing more projects like this, you can purchase Sams Teach Yourself PHP, MySQL and Apache All in One.

This chapter is from the book

Displaying the Topic List

Now that you have a topic and at least one post in your database, you can display this information and let people add new topics or reply to existing ones. In Listing 21.4, you take a step back and create a page that lists all the topics in the forum. This page shows the basic information of each topic and provides the user with a link to add a new topic; you have already created the form and script for that. The code in Listing 21.4 represents an entry page for your forum.

Although Listing 21.4 looks like a lot of code, it’s actually many small, simple concepts you’ve already encountered, starting with the include() function and database connection function in lines 2–3.

Listing 21.4 Topic Listing Script

1: <?php
2: include("ch21_include.php");
3: doDB();
5: //gather the topics
6: $get_topics_sql = "SELECT topic_id, topic_title, 
7:          DATE_FORMAT(topic_create_time, ‘%b %e %Y at %r’) AS 
8:          fmt_topic_create_time, topic_owner FROM forum_topics 
9:          ORDER BY topic_create_time DESC";
10: $get_topics_res = mysqli_query($mysqli, $get_topics_sql) 
11:          or die(mysqli_error($mysqli));
13: if (mysqli_num_rows($get_topics_res) < 1) { 
14:  //there are no topics, so say so
15:  $display_block = "<p><em>No topics exist.</em></p>";
16: } else { 
17:  //create the display string
18:  $display_block = "
19:  <table cellpadding=\ "3\ " cellspacing=\ "1\ " border=\ "1\ ">
20:  <tr>
21:  <th>TOPIC TITLE</th>
22:  <th># of POSTS</th>
23:  </tr>";
25:  while ($topic_info = mysqli_fetch_array($get_topics_res)) { 
26:    $topic_id = $topic_info[‘topic_id’];
27:    $topic_title = stripslashes($topic_info[‘topic_title’]);
28:    $topic_create_time = $topic_info[‘fmt_topic_create_time’];
29:    $topic_owner = stripslashes($topic_info[‘topic_owner’]);
31:    //get number of posts
32:    $get_num_posts_sql = "SELECT COUNT(post_id) AS post_count FROM
33:               forum_posts WHERE topic_id = ‘".$topic_id."’";
34:    $get_num_posts_res = mysqli_query($mysqli, $get_num_posts_sql) 
35:               or die(mysqli_error($mysqli));
37:    while ($posts_info = mysqli_fetch_array($get_num_posts_res)) { 
38:      $num_posts = $posts_info[‘post_count’];
39:    } 
41:    //add to display
42:    $display_block .= "
43:    <tr>
44:    <td><a href=\ "showtopic.php?topic_id=".$topic_id."\ "><strong>".
45:    $topic_title."</strong></a><br/>
46:    Created on ".$topic_create_time." by ".$topic_owner."</td>
47:    <td align=center>".$num_posts."</td>
48:    </tr>";
49:   } 
50:   //free results
51:   mysqli_free_result($get_topics_res);
52:   mysqli_free_result($get_num_posts_res);
54:   //close connection to MySQL
55:   mysqli_close($mysqli);
57:   //close up the table
58:   $display_block .= "</table>";
59: } 
60: ?>
61: <html>
62: <head>
63: <title>Topics in My Forum</title>
64: </head>
65: <body>
66: <h1>Topics in My Forum</h1>
67: <?php echo $display_block; ?>
68: <p>Would you like to <a href="addtopic.html">add a topic</a>?</p>
69: </body>
70: </html>

Lines 6–11 show the first of the database queries, and this particular one selects all the topic information in order by descending date. In other words, these lines gather the data in such a way that the topic that was created most recently will appear at the top of the list. In the query, notice the use of the date_format() function to create a much nicer date display than the raw value stored in the database.

Line 13 checks for the presence of any records returned by the query. If no records are returned, and therefore no topics are in the table, you’ll want to tell the user. Line 15 creates this message. At this point, if no topics existed, the script would break out of the if...else construct and be over with; the next action would occur at line 61, which is the start of the static HTML. If the script ended here, the message created in line 15 would be printed in line 67.

If, however, you have topics in your forum_topics table, the script continues at line 16. At line 18, a block of text is assigned to the $display_block variable, containing the beginnings of an HTML table. Lines 19–23 set up a table with two columns: one for the title and one for the number of posts. At line 25, you begin to loop through the results of the original query.

The while loop in line 25 says that while there are elements to be extracted from the resultset, extract each row as an array called $topic_info, and use the field names as the array element to assign the value to a new variable. So, the first element the script tries to extract is the topic_id field, on line 26. It assigns the value of $topic_info[‘topic_id’] to the $topic_id variable, meaning that it gets a local value for $topic_id from an array called $topic_info, containing a field called topic_id. Continue doing this for the $topic_title, $topic_create_time, and $topic_owner variables in lines 27–29. The stripslashes() function removes any escape characters that were input into the table at the time of record insertion.

Lines 32–35 issue another query, in the context of the while loop, to get the number of posts for that particular topic. In line 42, the script continues the creation of the $display_block string, using the concatenation operator (.=) to make sure that this string is tacked on to the end of the display string we have built so far. In line 44, you create the HTML table column to display the link to the file that will show the topic (showtopic.php) and print the topic owner and creation time.

The second HTML table column, on line 47, shows the number of posts. The script breaks out of the while loop on line 49, and in line 58 adds the last bit to the $display_block string to close the table. The remaining lines print the HTML for the page, including the value of the $display_block string.

If you save this file as topiclist.php and place it in your web server document root, and if you have topics in your database tables, you might see something like Figure 21.4.

Figure 21.4

Figure 21.4 Topics are available.

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