Always redirect to HTTPS with Codeigniter

Within config\hooks.php I added the lines.

$hook['post_controller_constructor'][] = array(
    'function' => 'redirect_ssl', 
    'filename' => 'ssl.php', 
    'filepath' => 'hooks'
);

In the hooks folder, I created the file ssl.php with the following function:

function redirect_ssl() {
    $CI =& get_instance();
    $class = $CI->router->fetch_class();
    $exclude =  array('client');  // add more controller name to exclude ssl.
    if(!in_array($class,$exclude)) {
        // redirecting to ssl.
        $CI->config->config['base_url'] = str_replace('http://', 'https://', $CI->config->config['base_url']);
        if ($_SERVER['SERVER_PORT'] != 443) redirect($CI->uri->uri_string());
    } else {
        // redirecting with no ssl.
        $CI->config->config['base_url'] = str_replace('https://', 'http://', $CI->config->config['base_url']);
        if ($_SERVER['SERVER_PORT'] == 443) redirect($CI->uri->uri_string());
    }
}