Network_Container incorrectly validates site_id using blog_id check

[ericbrissette]

The Network_Container class has a bug where it confuses WordPress multisite's site_id (network ID) with blog_id (individual site/blog ID). This causes the container to fail when setting a valid network ID via SITE_ID_CURRENT_SITE.

Environment

• WordPress Multisite installation
• Carbon Fields version: 3.6.9
• WordPress version: 6.8.3

Steps to Reproduce

1. Set up a WordPress multisite installation with multiple, or a single network with a site_id of something other than 1 (e.g., 6)
2. In wp-config.php, define the network ID constant (e.g., define('SITE_ID_CURRENT_SITE', 6);)
3. Verify in the database that the network exists in the wp_site table with id = 6 and that there is no blog with a blog_id = 6
4. Create a Network_Container in Carbon Fields
5. Observe the error: The specified site id #6 does not exist

Expected Behavior

The Network_Container should accept a valid network ID from SITE_ID_CURRENT_SITE and validate it against the wp_site table (network table), not the wp_blogs table.

Actual Behavior

The container throws an Incorrect_Syntax_Exception stating the site doesn't exist, even when the network ID is valid.

Root Cause

The bug is in the site_exists() method in Network_Container.php (lines 51-58):

protected function site_exists( $id ) {
    if ( ! function_exists( 'get_blog_status' ) ) {
        return false;
    }

    $blog_domain = get_blog_status( $id, 'domain' );
    return ! empty( $blog_domain );
}

The problem: get_blog_status() expects a blog_id (from wp_blogs table), but the method receives a site_id (network ID from wp_site table). These are different entities in WordPress multisite:

• site_id: Network ID (stored in wp_site table)
• blog_id: Individual site/blog ID (stored in wp_blogs table)

The class variable is named $site_id, the constant is SITE_ID_CURRENT_SITE, and the class is Network_Container, all suggesting this should work with network IDs, not blog IDs.

Suggested Fix

The site_exists() method should validate network IDs, not blog IDs. Here's a corrected implementation:

protected function site_exists( $id ) {
    global $wpdb;
    
    // Check if the network (site) exists in wp_site table
    $network = $wpdb->get_row( $wpdb->prepare(
        "SELECT id FROM {$wpdb->site} WHERE id = %d",
        $id
    ) );
    
    return ! empty( $network );
}

Impact

This bug prevents Carbon Fields Network Containers from working correctly on multisite installations where:

• There are multiple networks
• The network ID doesn't happen to match an existing blog ID
• Custom network configurations are used