MB Relationships - Database error for relationship between users_to_posts

This is a debug site.
I did not use the builder.
The only relationship that is defined is the one that you see in the code example above.

I don't like sharing credentials unless absolutely necessary.
Have you tried to replicate the issue first? And it did not occur?

Hello,

The only relationship that I register is the one described in the initial ticket.
But I have done some further testing and I suspect it has to do with the php version.
With php 7 the problem occurs.
With php 8 the problem does not occur.

Can you confirm this?

Hello,

Ok, in that case it was coincidence that the error occurred only on servers with PHP 8.

I did some further testing on my local host.
I will try to replicate these steps on a live server, so I can give you access to it.

On my localhost I have:
PHP: Version 7.4.29
MYSQL: 10.4.24-MariaDB

I installed two clean WordPress instances: one single site and one multi-site.

The only plugins that are active are

• Metabox
• MB Relationships
• MB Relationships Debug (plugin that registers the relationship)

The debug plugin only registers one relationship:

add_action('mb_relationships_init', function () {
    MB_Relationships_API::register([
        'id'   => 'users_to_posts',
        'from' => [
            'object_type'   => 'user',
            'admin_column'  => [
                'title'         => 'Posts',
            ],
        ],
        'to'   => [
            'object_type'   => 'post',
            'post_type'     => 'post',
            'admin_column'  => [
                'title'         => 'Users',
            ],
        ]
    ]);
});

On both WordPress installations I get two Metaboxes on the post edit screen:

Also I get the following error message:

WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'mbr.order_to' at line 6 for query \n\t\t\t\tSELECT wp_users.ID , mbr.to\n\t\t\t\tFROM wp_users INNER JOIN wp_usermeta ON ( wp_users.ID = wp_usermeta.user_id ) INNER JOIN wp_2_mb_relationships AS mbr ON (mbr.from = wp_users.ID AND mbr.type = 'users_to_posts' AND mbr.to IN (1)) \n\t\t\t\tWHERE 1=1 AND ( \n wp_usermeta.meta_key = 'wp_2_capabilities'\n)\n\t\t\t\tmbr.order_to\n\t\t\t\t\n\t\t\t made by WP_List_Table->display, WP_List_Table->display_rows_or_placeholder, WP_Posts_List_Table->display_rows, WP_Posts_List_Table->_display_rows, WP_Posts_List_Table->single_row, WP_List_Table->single_row_columns, WP_Posts_List_Table->column_default, do_action('manage_post_posts_custom_column'), WP_Hook->do_action, WP_Hook->apply_filters, MBR_Admin_Columns->post_to_column_data, MBR_Admin_Columns->get_column_data, MBR_Admin_Columns->get_user_items, get_users, WP_User_Query->__construct, WP_User_Query->query, referer: http://localhost/wp-dev-2/mb-relationship-debug/wp-admin/post.php?post=1&action=edit

Nevermind, I tested it myself on https://instawp.com/ with PHP 7.4 and the error did not occur.
I will try to debug some further, but could you please let the developers know of the error message?
Maybe they have an idea what might cause such an error.