}
add_action('add_meta_boxes', 'add_schema_meta_box');
// Display Meta Box with Existing + Add More
function display_schema_meta_box($post) {
wp_nonce_field('save_schema_meta_box_nonce', 'schema_meta_box_nonce');
$schema_data = get_post_meta($post->ID, '_schema_data', true);
// If it's a string (old single field), convert to array
if (!is_array($schema_data)) {
$schema_data = [$schema_data];
}
?>