// Redirect URLs containing index.php to non-index.php versions
function redirect_index_php_urls() {
    if (strpos($_SERVER['REQUEST_URI'], '/index.php/') !== false) {
        $url_parts = explode('/index.php/', $_SERVER['REQUEST_URI']);
        if (count($url_parts) == 2) {
            $redirect_url = home_url() . '/' . $url_parts[1];
            wp_redirect($redirect_url, 301);
            exit;
        }
    }
}
add_action('template_redirect', 'redirect_index_php_urls');