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. Maintain a database of users visiting your site: You can enable user authentication, e-mail your users to give them exciting news, sign them up for newsletters, and so on. . Create an online e-commerce site: Create shopping carts where users can store the merchandise they will purchase. (This can be daunting many choose to use a third-party shopping cart application.) . Create an online discussion forum where your users can go to discuss how wonderful your site looks! These are just a few ideas. In fact, you are going to see how to do each of these things over the course of upcoming chapters. With a little imagination, you can come up with solutions to almost any problem you might face in building your site. If any of the ideas presented in this chapter are difficult for you to grasp, that s okay. It is a lot of material, especially if you are a beginning programmer. The great thing about a book is that you can keep coming back! You will also be revisiting many of these concepts in later chapters. For example, in Chapter 16 where you learn to build your own forum, you will go through database normalization again on a new set of databases. You will also have many more opportunities to create SQL queries, some familiar and some new. For now, take some time to play with your new toy, the Character Database. You have the basic knowledge for creating even the most complex sites. You have the first incarnation installed on your server. Now all you need to do is let all of your friends and family know about your cool new site. If only you knew how to send e-mails using PHP. Well, we ll handle that in Chapter 11. Exercises See how you might accomplish the following tasks: 1. Add a costume description field to the character record, and provide a way to modify the costume description. 2. Modify the character listing to display the characters locations alongside their powers. 324 Chapter 10
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Remember what you did with the Powers field? Ditto all of that for the Enemies field. The only difference here is that if there are no values in the $charlist variable (list of all characters except the chosen character), the Enemies field will not show up on the form.
Enemies:
(Ctrl-click to
select multiple
enemies) ; $value) { echo $valuen ; } If the character entry form is not in Update mode, then the script will hide the Delete Character button (you can t delete a character you haven t created yet):      Finally, the character ID is not passed through any form fields, so you create a hidden field to hold that information. You need that ID if you are going to update an existing character. Of course, if you are creating a new character, then the ID will be created for you when you insert all the appropriate data. > Summary Whew! This chapter covered a lot of ground. You learned about how to plan the design of your application, including database design. You learned how to normalize your data, so that it can easily be linked and manipulated. You created a brand new database for your Web site and started building your Web site by creating tables and creating the Web application needed to access and update those tables. Congratulations! You just created your first, fully functioning Web application with a relational database backend. (That s going to look so good on your resume.) This chapter is only the beginning, however. With the knowledge you gained here, you can create almost any application you desire. Here are some examples of what you could do: . Content Management (CMS): Create a data entry systems that will allow users and administrators to alter the content of the Web site and your database without knowing any HTML. 323 Building Databases
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You next build the table in HTML, and insert values into the appropriate places as defaults. This is how you fill in the fields with character data. Note how the script checks to see if the variable is set before echoing it to the page. If it didn t, and the error reporting for PHP was set to E_ALL, there might be a warning printed to the screen if $ch didn t contain a value. Checking is usually a good idea if you aren t certain a variable will be set. Character Name: >

Now you build the Powers select field. As the script loops through each power in the $pwrlist array (which contains all powers), it concatenates the $powers array value for that power ( selected ). If that power s key (from $pwrlist) doesn t exist in the $powers array, $powers[$key] will simply be blank instead of selected. In this way, the script builds a field of all powers where the character s chosen powers are selected in the list. Neato, huh? Powers:
(Ctrl-click to
select multiple
powers) $value) { echo $valuen ; } ?>

Note the [] in the select name attribute. That is necessary for PHP to recognize the variable as an array when it gets POSTed to the next page. This is a requirement for any field that might post with multiple values. The following code creates a set of radio buttons for good and evil. The character s alignment is selected with the checked attribute. > good
> evil

322 Chapter 10
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AND c.lair_id = l.id . AND c.id = $char ; $result = mysql_query($sql) or die(mysql_error()); $ch = mysql_fetch_array($result); Once the script determines there was a record retrieved, it alters the default variables to reflect the edited document. The background is green, and you are Updating rather than Creating. if (is_array($ch)) { $subtype = Update ; $tablebg = #EEFFEE ; $subhead = Edit data for . $ch[ alias ] . and click $subtype Character. ; The next SQL statement retrieves all powers associated with this character. All you really need is the ID so that you can create a $powers array with each element containing the word selected. This will be used in the Powers field on the form, so that each power assigned to the character will be automatically selected. $sql = SELECT p.id . FROM char_main c . JOIN char_power p . JOIN char_power_link pk . ON c.id = pk.char_id . AND p.id = pk.power_id . WHERE c.id = $char ; $result = mysql_query($sql) or die(mysql_error()); if (mysql_num_rows($result) > 0) { while ($row = mysql_fetch_array($result)) { $powers[$row[ id ]] = selected ; } } Now you do exactly the same thing with the character s enemies. Note the similarity in this SQL statement to the one in charlist.php. The only difference is that you want only the enemies that match your character. // get list of character s enemies $sql = SELECT n.id . FROM char_main c . JOIN char_good_bad_link gb . JOIN char_main n . ON (c.id = gb.good_id AND n.id = gb.bad_id) . OR (n.id = gb.good_id AND c.id = gb.bad_id) . WHERE c.id = $char ; $result = mysql_query($sql) or die(mysql_error()); if (mysql_num_rows($result) > 0) { while ($row = mysql_fetch_array($result)) { $enemies[$row[ id ]] = selected ; } } 321 Building Databases
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charedit.php This file does double-duty, so it s a little longer. But a lot of it is HTML, and much of what it does you have already done before, so this shouldn t be too difficult. The default functionality of this page is New Character mode. If there is a value in $char other than 0, the script will pull the data and change the default values. if (!isset($_GET[ c ]) || $_GET[ c ] == || !is_numeric($_GET[ c ])) { $char= 0 ; } else { $char = $_GET[ c ]; } $subtype = Create ; $subhead = Please enter character data and click . $subtype Character. ; $tablebg = #EEEEFF ; Next, the script gets all the powers, and puts them into an array to be accessed later (when building the power select field on the form). $sql = SELECT id, power FROM char_power ; $result = mysql_query($sql) or die(mysql_error()); if (mysql_num_rows($result) > 0) { while ($row = mysql_fetch_array($result)) { $pwrlist[$row[ id ]] = $row[ power ]; } } All characters except the chosen character will be pulled from the database to be used for the Enemies field. If the character ID is not valid, then all characters will be pulled for the Enemies field. $sql = SELECT id, alias FROM char_main WHERE id != $char ; $result = mysql_query($sql) or die(mysql_error()); if (mysql_num_rows($result) > 0) { $row = mysql_fetch_array($result); $charlist[$row[ id ]] = $row[ alias ]; } If there is a character id, the script attempts to pull the data from the database. This SQL statement is also a JOIN, although the JOIN keyword is not used. You can identify such a JOIN because there are two or more tables, and the WHERE keyword is matching columns from each of the tables. The JOIN in this case is implied. Once all the tables are joined, all the appropriate fields are pulled as long as the character ID in the character table matches $char. If there is no match, no records will be returned. If there is a match, one record is returned and the row is stored in $ch. if ($char != 0 ) { $sql = SELECT c.alias, c.real_name AS name, c.align, . l.lair_addr AS address, z.city, z.state, z.id AS zip . FROM char_main c, char_lair l, char_zipcode z . WHERE z.id = l.zip_id . 320 Chapter 10
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$table .=
; $table .= Alias ; $table .= ; $table .= Name Alignment Powers

; $table .= Enemies

; Next, you alternate the background colors of the table, to make it a little easier to read. // build each table row $bg = ; while ($row = mysql_fetch_array($result)) { $bg = ($bg== F2F2FF ? E2E2F2 : F2F2FF ); Remember the power and enemy arrays you built earlier? You use the character s ID to grab the list of values and put them into a variable to be inserted shortly into the appropriate table cell. $pow = ($powers[$row[ id ]]== ? none :$powers[$row[ id ]]); if (!isset($enemies) || ($enemies[$row[ id ]]== )) { $ene = none ; } else { $ene = $enemies[$row[ id ]]; } The table is built, row by row, inserting the appropriate data in each cell; then it s closed: $table .=
. . $row[ alias ]. . $row[ name ] . . $row[ align ] . . $pow .

.
. $ene .

; } $table .=

; Just for kicks, and to make them more visible, the script changes the color of the good and evil values in the table. This isn t necessary, but it makes the values pop out more. $table = str_replace( evil , evil , $table); $table = str_replace( good , good , $table); This variable contains either the

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