Custom Post type sort order not working in the admin area

Question

I have a WordPress site that has a couple of custom post types. None of these custom post types allow me to sort the posts alphabetically or by date in the admin area.

I have looked all over online to try and work this out but I can't seem to find anything that works.

Do I need to apply an action on load of posts in the admin area?

Answer 1

The 'title' and 'date' columns are WordPress default tables (even for CPTs) so they should be automatically sortable, unless those columns have been replaced.

For custom columns there is a hook for registering a column as 'sortable': https://developer.wordpress.org/reference/hooks/manage_this-screen-id_sortable_columns/

//Filter is 'manage_edit-{custom post type}_sortable_columns
//or more generally 'manage_{screen id}_sortable_columns
add_filter( 'manage_edit-cpt_sortable_columns', 'wpse221267_cpt_sortable_columns' );
function wpse221267_cpt_sortable_columns( $columns ) {
    //$columns is an array indexed by column identifier
    //and the value is a sort identifier. This sets the orderby parameter (see below)
    //Each element in $columns corresponds to a sortable column
    $columns['column_id'] = 'sort_identifier';
    return $columns;
}

However, this only handles the user interface: it doesn't actually implement the sort. To do that you would need to intercept the query at pre_get_posts:

add_action( 'pre_get_posts', 'wpse221267_column_orderby' );  
function wpse221267_column_orderby( $query ) {  

    //Some sanity checking, you may want to check for screen ID too.        
    if( ! is_admin() ) {
        return;  
    }

    //This value will be determined by the column clicked
    //and its associated sort identifier (see above!)
    $orderby = $query->get( 'orderby');  
    $order   = $query->get( 'order' );

    if( 'sort_identifier' == $orderby ) {  
        //Modify $query to sort by $orderby and $order.
    }  
}