$config = parse_ini_file('config.ini'); // load existing configuration settings $config['DB_HOST'] = 'localhost'; // add or update 'DB_HOST' setting $config['DB_USER'] = 'myuser'; // add or update 'DB_USER' setting $config['DB_PASS'] = 'mypassword'; // add or update 'DB_PASS' setting $config_str = ""; // create empty string to store new configuration file contents // loop through configuration settings and add them to $config_str foreach($config as $key => $value){ $config_str .= "$key=$value\n"; } file_put_contents('config.ini', $config_str); // save configuration fileThis example adds three database settings to an existing configuration file (`config.ini`): DB_HOST, DB_USER, and DB_PASS. It does this by first loading the existing configuration file using the `parse_ini_file` function, and then updating the relevant configuration settings using array notation. Finally, the new configuration settings are saved to the configuration file using the `file_put_contents` function. In terms of package libraries, this example does not require any external libraries as it uses built-in PHP functions. However, there are many PHP libraries that provide more powerful and flexible configuration management capabilities, such as the popular Symfony Config component.