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The first step is connecting to the MySQL database to retrieve the data. This article is focused on JavaScript, so I won't explain how the following code works; you'll need to learn how to connect to a MySQL database in more detail on your own.
<?php
$user = "admin";
$pass = "adminpass";
$host = "localhost";
$conn = mysql_connect($host, $user, $pass) or die("Unable to connect to MySQL.");
$db = mysql_select_db("pets",$conn) or die("Could not select the database.");
mysql_close($db);
?>
Once you've connected to the database, you'll retrieve the information with a query as below:
<?php
$user = "admin";
$pass = "adminpass";
$host = "localhost";
$conn = mysql_connect($host, $user, $pass) or die("Unable to connect to MySQL.");
$db = mysql_select_db("pets",$conn) or die("Could not select the database.");
$result = mysql_query("SELECT * FROM `pets`");
if(mysql_num_rows ($result) == 0){
die ('Error: no data found in the database.');
}
while ($row = mysql_fetch_assoc($result)){
echo 'Pet: '.$row['pet'].', tasks: '.$row['tasks'].'. ';
}
mysql_close($db);
?>
This gives you the information you want, but it isn't output properly . We need to change the PHP to spit out the data as XML, not plain text. There are several changes we must make in order for this to occur.
<?php
header('Content-Type: text/xml');
echo '<?xml version="1.0" encoding="UTF-8"?>';
echo "\n<data>\n<pets>\n";
$user = "admin";
$pass = "adminpass";
$host = "localhost";
$conn = mysql_connect($host, $user, $pass) or die("Unable to connect to MySQL.");
$db = mysql_select_db("pets",$conn) or die("Could not select the database.");
$result = mysql_query("SELECT * FROM `pets`");
if(mysql_num_rows ($result) == 0){
die ('Error: no data found in the database.');
}
while ($row = mysql_fetch_assoc($result)){
echo '<'.$row['pet'].' tasks="'.$row['tasks'].'" />'."\n";
}
echo "</pets>\n</data>";
mysql_close($db);
?>
Let's take the above, one line at a time, and analyze how it's outputting the XML. I've color-coded each line to make it easier to understand.
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Now that we've gotten PHP to output the XML, all we have to do to update the XML is login to our MySQL database and make the changes we want. Pretty cool, agreed? We can use exactly the same JavaScript as in the last article to retrieve this data, because the XML output is exactly the same.
You can extend this further by simply using XML to store and retrieve data. In other words, you can use PHP to write to your XML file and then have JavaScript read that XML file. With Ajax, you can also periodically check to see if that XML file has been updated and, if so, update the page accordingly.
Jonathan Fenocchi is a Web developer who primarily works in the fields of Web Design with CSS, client-side scripting with JavaScript, and server-side scripting with PHP. His web site is located at: http://www.slightlyremarkable.com.
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