How can I create a shortcode to show the number of posts of actual day?

I tried some codes, and I think finally works after several tries:

function ts_day_f() {
    $posts= get_posts(array(
            'numberposts' => -1,
            'post_status' => 'publish',
            'orderby' => 'date',
            'order'   => 'DESC',
            'date_query'    => array(
                'column'  => 'post_date',
                'after'     => 'today',
                'before'    => 'tomorrow - 1 second',
            )
        ));

    if ( is_user_logged_in()) {
        //return count($posts);
        $c = count($posts);

        return "Today: <span style=\"font-size: 1.5em;\">" .$c. "</span> posts.";
    }
    else  {
        return $null;
    }
}

add_shortcode('ts_day','ts_day_f');

Additionally with the function to show only to users log in.