Why Does My CodeIgniter Application Show a \'Unable to Connect to Server\' Database Error and How Can I Fix It?

CodeIgniter Database Connection Error: "Unable to Connect to Server" Resolved

In CodeIgniter, changing the database driver from MySQL to MySQLi sometimes results in an error message stating "Unable to connect to your database server using the provided settings." This error typically indicates an issue with the database configuration.

Troubleshooting the Error

As suggested by the user's response, the issue may lie in the PHP configuration. To debug the connection, add the following snippet to the end of the config/database.php file:

...
echo '<pre class="brush:php;toolbar:false">';
print_r($db['default']);
echo '

'; echo 'Connecting to database: ' .$db['default']['database']; $dbh=mysql_connect ( $db['default']['hostname'], $db['default']['username'], $db['default']['password']) or die('Cannot connect to the database because: ' . mysql_error()); mysql_select_db ($db['default']['database']); echo '
'; echo 'Connected OK:' ; die( 'file: ' .__FILE__ . ' Line: ' .__LINE__);

Analyzing the Output

Once this script is executed, it will output:

• Database settings
• Database connection status
• Error message (if any)

If there is a connection issue, the error will be displayed. Examine the error message to identify the cause of the problem.

Possible Solutions

• Incorrect Database Connection Settings: Ensure that the database hostname, username, password, and database name are correct.
• Firewall or Network Restrictions: Make sure the web server has access to the database server and the port used for the connection.
• PHP Configuration Issues: Ensure that PHP has MySQLi support enabled and that the extension is installed and loaded.
• Database Server Issues: Check the database server status to ensure it is running and accepting connections.
• Mismatched Database Versions: Ensure that the MySQLi version used in the PHP configuration is compatible with the MySQL server version.

By following these steps and debugging the database connection, you can resolve the "Unable to connect to server" error in CodeIgniter.

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