The first thing you need to do is connect to the database and check to make sure there's a connection. Including the file that you set up to store your connection information allows you to use the variables instead of hardcoded values when you call the mysql_connect function, as shown in Example 9-4.

Example 9-4.  Including the connection values and calling mysql_connect

<?php
include('db_login.php');
$connection = mysql_connect($db_host, $db_username, $db_password);
if (!$connection){
die ("Could not connect to the database: <br />". mysql_error());
}
?>

The mysql_connect function takes the database host, username, and password as parameters. If the connection is successful, a link to a database is returned. FALSE is returned if a connection can't be made. Check the return value from the function to make sure there's a connection. If there's a problem, such as an incorrect password, print out a polite warning and the reason for the error using mysql_error.

Instead of simply echoing an error message, use the die function to display the error, and then stop the program, Not being able to access the database makes most database-driven pages fairly useless and prevents the user from seeing numerous errors.

Notice that we didn't specify the database name yet.

One error you may get is:

  Fatal error: Call to undefined function mysql_connect() in C:Program FilesApache
  GroupApache2htdocstest.php on line 4

This occurs because PHP 5.1.2 for Windows was downloaded, and MySQL support was not included by default. To fix this error, copy the php_mysql.dll file from the ext/ directory of the PHP zip file to C:php, and then edit lines 461 and 589 of C: WINDOWSphp.ini. This will change the extension to include the directory to C:/php and uncommenting the MySQL extension line, respectively.

You'll need to restart Apache, and then MySQL support will be enabled.