In this section, we'll see how we can use all the tools at our
disposal to allow visitors to our site to add their own jokes to
the database. If you enjoy a challenge, you might want to try to
figure this out on your own before you read any further. There is
precious little new material in this section. It's mostly just a
sample application of everything we've learned so far.
If you want to let visitors to your site type in new jokes,
you'll obviously need a form. Here's the code for a form that
will fit the bill:
<form action="<?=$PHP_SELF?>" method="post">
<p>Type your joke here:<br />
<textarea name="joketext" rows="10" cols="40" wrap></textarea><br />
<input type="submit" name="submitjoke" value="SUBMIT" /></p>
</form>
As we've seen before, this form, when submitted, will load the
very same page (due to the use of the $PHP_SELF
variable for the form's action attribute), but with
two variables attached to the request. The first,
$joketext, will contain the text of the joke as
typed into the text area. The second, $submitjoke,
will always contain the value "SUBMIT", which can be
used as a sign that a joke has been submitted.
To insert the submitted joke into the database, we just use
mysql_query to run an INSERT query,
using the $joketext variable for the value to be
submitted:
if ($submitjoke == "SUBMIT") {
$sql = "INSERT INTO Jokes SET
JokeText='$joketext',
JokeDate=CURDATE()";
if (@mysql_query($sql)) {
echo("<p>Your joke has been added.</p>");
} else {
echo("<p>Error adding submitted joke: " .
mysql_error() . "</p>");
}
}
The one new trick in this whole example appears in the SQL code
here. Note the use of the MySQL function CURDATE()
to assign the current date as the value of the
JokeDate column to be inserted into the database.
MySQL actually has dozens of these functions, but we'll only
introduce them as required. For a complete function reference,
refer to the MySQL Reference Manual.
We now have the code that will allow a user to type a joke and
add it to our database. All that remains is to slot it into our
existing joke viewing page in a useful fashion. Since most users
will only want to view our jokes, we don't want to mar our page
with a big, ugly form unless the user expresses an interest in
adding a new joke. For this reason, our application is well
suited for implementation as a multi-purpose page. Here's the
code (available as jokes.php in the
code archive):
<html>
<head>
<title> The Internet Joke Database </title>
</head>
<body>
<?php
if (isset($addjoke)): // If the user wants to add a joke
?>
<form action="<?=$PHP_SELF?>" method="post">
<p>Type your joke here:<br />
<textarea name="joketext" rows="10" cols="40" wrap></textarea><br />
<input type="submit" name="submitjoke" value="SUBMIT" /></p>
</form>
<?php
else: // Default page display
// Connect to the database server
$dbcnx = @mysql_connect("localhost", "root", "mypasswd");
if (!$dbcnx) {
echo( "<p>Unable to connect to the " .
"database server at this time.</p>" );
exit();
}
// Select the jokes database
if (! @mysql_select_db("jokes") ) {
echo( "<p>Unable to locate the joke " .
"database at this time.</p>" );
exit();
}
// If a joke has been submitted,
// add it to the database.
if ($submitjoke == "SUBMIT") {
$sql = "INSERT INTO Jokes SET
JokeText='$joketext',
JokeDate=CURDATE()";
if (@mysql_query($sql)) {
echo("<p>Your joke has been added.</p>");
} else {
echo("<p>Error adding submitted joke: " .
mysql_error() . "</p>");
}
}
echo("<p> Here are all the jokes in our database: </p>");
// Request the text of all the jokes
$result = @mysql_query("SELECT JokeText FROM Jokes");
if (!$result) {
echo("<p>Error performing query: " . mysql_error() . "</p>");
exit();
}
// Display the text of each joke in a paragraph
while ( $row = mysql_fetch_array($result) ) {
echo("<p>" . $row["JokeText"] . "</p>");
}
// When clicked, this link will load this page
// with the joke submission form displayed.
echo("<p><a href='$PHP_SELF?addjoke=1'>Add a Joke!</a></p>");
endif;
?>
</body>
</html>
There we go! With a single file that contains a little PHP code
we're able to view existing jokes, and add jokes to, our MySQL
database.
A Challenge
As homework, see if you can figure out how to put a link labeled
"Delete this Joke" next to each joke on the page that, when
clicked, will remove that joke from the database and display the
updated joke list. Here are a few hints to get you started:
- You'll still be able to do it all in a single multi-purpose
page.
- You'll need to use the SQL
DELETE command, which
we learned about in Chapter 2.
- This is the tough one. To delete a particular joke, you'll
need to be able to uniquely identify it. The
ID
column in the Jokes table was designed to serve this
purpose. You're going to have to pass the ID of the joke to be
deleted with the request to delete a joke. The query string of
the "Delete this Joke" link is a perfect place to put this value.
If you think you have the answer, or if you'd just like to see
the solution, advance to the next page. Good luck!
» 
Comment and Contribute
