Whilsts@Shaon的答案完全正确，我认为你真的不应该把配置设置作为全局变量，而应该使用常量。

/* Constants are in the global scope, but can only be defined once. */
define( \'FEEDBURNER_USERNAME\', \'my_username\' );
define( \'FEEDBURNER_PASSWORD\', \'my_password\' );

function get_feedburner_config( $option = null )
{
    $config = get_option( \'feedburner\' );
    $config = wp_parse_args( $config, array(
        \'username\' => \'default\',
        \'password\' => \'default\'
    ));

    if ( $option )
        return isset( $config[ $option ] ) ? $config[ $option ] : \'\';

    return $config;
}