Having a variable based on $post_count increase when i move to the next page of results

Question

I couldn't figure out the best way to write the title, so first of all I hope you understood what i was trying to get across. I have a snippet of code on my template page that fires after the wp_query to display a heading as such:

showing x of y results for ...

and the code:

elseif ($size_option&&!$color_option&&!$genre_option) {
echo '<h3>Showing ' . $wp_query->post_count . ' of ' . $wp_query->found_posts . '    results for ' . $size_name . ', all colors, all genres</h3>';}

As such it will show something like - showing 12 of 17 results for ...

However the issue is i have my posts_per_page set to 12. So when i go to page 2 (for a query that results in found_posts being 17), we get - showing 5 of 17 results for ...

Which is just illogical.

My question is how could i get it to show the following for once again, a total of 17 posts:

On page 1 - showing 1-12 of 17 results for...

On page 2 - showing 13-17 of 17 results for...

I have an idea of what i should use, but no idea on how to go about it. Im guessing i need to implement some kind of count, based on the 'paged'=> $paged arg from my wp_query.

Any help would be wondeful. Thank you, once again!

Mike

as requested by Johannes, my query :

$wp_query = new WP_Query ( array(
                                'post_type' => 'tshirt',
                                'posts_per_page' => 12,
                                'paged'=> $paged,
                                'colors' => $color_option,
                                'size' => $size_option,
                                'genres' => $genre_option));

Answer 1

Given your posted query and that you seem to still be trying to figure it out:

First, off you should not use $wp_query = new WP_Query ();, since $wp_query is a global wordpress core object. Use any other variable to store the custom query in, $the_query = new WP_Query (); for instance.

That being said, the below code does what you want (if you did rename the query-storing variable $the_query).

$current_page = $the_query->query_vars['paged'];
$per_page = $the_query->query_vars['posts_per_page'];
$total_posts = intval($the_query->found_posts);
$first_paged_post = (($current_page - 1) * $per_page) + 1;
$last_paged_post = min($current_page * $per_page, $total_posts);

echo '<h3>On page '.$current_page.' - Showing #'.$first_paged_post;
// to account for the case where the last page has only one post (i.e. total of 13, 25) 
if ($last_paged_post != $first_paged_post) {
    echo ' - #'.$last_paged_post;
}
echo ' of '.$total_posts.' results for '.$size_name.', all colors, all genres</h3>';

Edit, Note: While this is more copy&paste ready, it follows the same basic logic as Geert's snippet already provided.

Answer 2

I once calculated these variables for the Kohana Pagination library. If you replace the variables with your own you should be all set.

$current_first_item = (int) min((($current_page - 1) * $items_per_page) + 1, $total_items);
$current_last_item  = (int) min($current_first_item + $items_per_page - 1, $total_items);