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 21.3, we 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 21.3 represents an entry page for your forum.

Although Listing 21.3 looks like a lot of code, it's actually many small, simple concepts you've already encountered, starting with the database connection code in line 2.

Listing 21.3. Topic Listing Script

 1:  <?php 2:  //connect to server 3:  $mysqli = mysqli_connect("localhost", "joeuser", "somepass", "testDB"); 4: 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)); 12: 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:    $display_block = " 19:    <table cellpadding=\"3\" cellspacing=\"1\" border=\"1\"> 20:    <tr> 21:    <th>TOPIC TITLE</th> 22:    <th># of POSTS</th> 23:    </tr>"; 24: 25:    while ($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']); 30: 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)); 36: 37:        while ($posts_info = mysqli_fetch_array($get_num_posts_res)) { 38:            $num_posts = $posts_info['post_count']; 39:        } 40: 41:        //add to display 42:        $display_block .= " 43:        <tr> 44:        <td><a href=\"showtopic.php?topic_\"><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); 53: 54:     //close connection to MySQL 55:     mysqli_close($mysqli); 56: 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 611 show the first of the database queries, and this particular one selects all the topic information in order by descending date. In other words, 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, and you would see something like Figure 21.4.

Figure 21.4. No topics found.


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 1923 set up a table with two columns: one for the title and one for the number of posts. At line 25, we 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 we try to extract is the topic_id field, on line 26. We assign the value of $topic_info['topic_id'] to the $topic_id variable, meaning that we get 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 2729. The stripslashes() function removes any escape characters that were input into the table at the time of record insertion.

In lines 3235 we issue another query, in the context of the while loop, to get the number of posts for that particular topic. In line 42, we continue 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, we create the HTML table column to display the link to the file that will show the topic (showtopic.php), and also print the topic owner and creation time.

The second HTML table column, on line 47, shows the number of posts. On line 49, we break out of the while loop, and in line 58 add 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 may see something like Figure 21.5.

Figure 21.5. Topics are available.





Sams Teach Yourself PHP, MySQL And Apache All in One
Sams Teach Yourself PHP, MySQL and Apache All in One (3rd Edition)
ISBN: 0672328739
EAN: 2147483647
Year: 2004
Pages: 327

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