I want to save order item category in order item meta. Got help from this answer https://stackoverflow.com/a/55575047/12183966 but i am getting an Internal Server Error on WooCommerce checkout.

Uncaught Error: Call to a member function get_items() on null

I can't figure out what i am doing wrong here. Any advice?

This is my code:

// Save item custom fields label and value as order item meta data
add_action('woocommerce_add_order_item_meta','save_in_order_item_meta', 10, 3 );
function save_in_order_item_meta( $item_id, $values, $cart_item_key ) {
    foreach ($order->get_items() as $item ) {
        $term_names = wp_get_post_terms( $item->get_product_id(), 'product_cat', ['fields' => 'names'] );
        // Output as a coma separated string
        $cat = implode(', ', $term_names);
        wc_add_order_item_meta( $item_id, 'category', $cat );
    }
}

CodePudding user response：

• woocommerce_add_order_item_meta hook is deprecated since WooCommerce 3. Use woocommerce_checkout_create_order_line_item instead
• $order is undefined in your code attempt

So you get:

function action_woocommerce_checkout_create_order_line_item( $item, $cart_item_key, $values, $order ) {
    // Get the product categories for this item
    $term_names = wp_get_post_terms( $item->get_product_id(), 'product_cat', array( 'fields' => 'names' ) );

    // Output as a coma separated string
    $item->update_meta_data( 'category', implode( ', ', $term_names ) );  
}
add_action( 'woocommerce_checkout_create_order_line_item', 'action_woocommerce_checkout_create_order_line_item', 10, 4 );

Note: add an underscore at the beginning of the meta key (like: _category) to set any meta value as hidden order item meta data, so it's only visible on admin order edit pages