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I would like to get the (one) post with the last ID, even if it is not the last post by date. The post belongs to a custom post type.

I need this to assign custom id numbers to my orders. When creating a new order, I am going to find the post with the largest ID, get its order number from its meta, increment it and assign it to the new one. I DO UPDATE order post when order gets changed in any way and update its date to make it appear at the top of the post list. Therefore, the last post by date that WP gets does not necessarily have the largest ID number. I would like to get the post with the largest post ID.

This is an example list of my post ids

3460 3465 3464 3463 3462 3461 3459

I need to get 3465

This is my code:

$args = array(
   'post_type' => 'my_order_cpt',
   'post_status' => array('confirmed', 'paid', ..... , 'closed'),
   'numberposts' => 1,
   'orderby' => 'ID',
   'order'   => 'DESC'
);
$numbers = get_posts($args);

However, this gives me the last post by date. In my exaple, it's 3460.

All the answers I found, e.g. here, describe getting the last post by date.

I know there's a way to do this with a wpdb query ("SELECT meta_value FROM wp_postmeta WHERE meta_key='[plugin_prefix]_order_number' ORDER BY CAST(meta_value AS UNSIGNED) DESC LIMIT 1" + checking if post is not a draft and not in trash) or by getting all posts of the post type and playing with the array, but is there a way with get_posts()? Maybe, with meta_query? The order number is a separate meta field named '[plugin_prefix]_order_number'.

  • Looks like this should work. There's no 'numberposts' parameter, so perhaps that's confusing things. Try 'posts_per_page' => 1 – mozboz Jul 14 at 17:15
  • Also, it shouldn't, but I wonder if 'orderby' => array( 'ID' => 'DESC' ) and remove order parameter makes any difference? – mozboz Jul 14 at 17:16
  • @mozboz Numberposts is an alias of post_per_page, see developer.wordpress.org/reference/functions/get_posts – tolkodelo Jul 14 at 17:17
  • Ah, nice. I didn't know that - usually refer to the WP_Query page for args – mozboz Jul 14 at 17:18
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    Normally the latest post has the largest ID. If that isn't the case for you, you might have a problem with your setup. Anyway, try retrieving only the post IDs using fields parameter in your query. Then sort that array and get the first index. – Abhik Jul 14 at 17:38
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Turns out, I was kind of wrong when I tried to get the largest ID. What I needed was to get posts by, and then to sort by, the order number itself! Here's what I came up with:

$num_args = array(
    'post_type' => 'my_store_order',
    'post_status' => array('mystatus_1', 'mystatus_2', 'mystatus_N'),
    'numberposts' => 1,
    'meta_query' => array(
        'my_clause' => array(
            'key' => 'my_order_number',
            'type' => 'numeric',
            'compare' => 'EXIST'
        )
    ),
    'orderby' => 'my_clause',
    'order' => 'DESC'
);

Also, since post meta is a string, I added 'type' => 'numeric' so when being sorted it would be treated as a number (1,2,10 vs 1,10,2)

This post helped me a lot

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