got stuck in WooCommerce & WordPress ( both latest versions ) with a little piece of code.

// What i want?

Some very similar option like “upselling” & cross-selling. If any customer want buy a product, like a stamp or something else should be able to choose some the correct hangtags who fits to the first product – like a stamp!

So far so good, figured it out with some lines of code, a new tab and an input_textfield. But typing in all these product_ID’s isn’t fun. With wc-product-search it should be easy and done in seconds. Grinding at least for more than 4 hours, but can’t get it working properly! It works so far but doesn’t update the meta if it got changed.

Is there any pro out there, who can provide some help?

/**
  * Add a custom product tab.
  */

 function matching_products_tab( $tabs) {
    $tabs['matching_products'] = array(
        'label'     => __( 'Matching Products', 'eva' ),
        'target'    => 'matching_products',
        'class'     => array( 'show_if_simple', 'show_if_variable'  ),
    );
    return $tabs;
 }
 add_filter( 'woocommerce_product_data_tabs', 'matching_products_tab' );


 /**
  * Contents of matching products tab
  */
 function matching_product_tab_content() {
 global $post, $woocommerce;
 ?><div id="matching_products" class="panel woocommerce_options_panel">
    <div class="options_group">
    <p class="form-field product_field_type">
    <label for="product_field_type"><?php _e( 'Product Select', 'woocommerce' ); ?></label>
    <select class="wc-product-search" multiple="multiple" style="width: 50%;" id="product_field_type" name="product_field_type[]" data-placeholder="<?php esc_attr_e( 'Search for a product&hellip;', 'woocommerce' ); ?>" data-action="woocommerce_json_search_products_and_variations" data-exclude="<?php echo intval( $post->ID ); ?>">
        <?php
            $product_field_type_ids = get_post_meta( $post->ID, '_product_field_type_ids', true );
            $product_ids = ! empty( $product_field_type_ids ) ? array_map( 'absint',  $product_field_type_ids ) : null;
            if ( $product_ids ) {
                foreach ( $product_ids as $product_id ) {
                    $product      = get_product( $product_id );
                    $product_name = woocommerce_get_formatted_product_name( $product );
                    echo '<option value="' . esc_attr( $product_id ) . '" selected="selected">' . esc_html( $product_name ) . '</option>';
                }
            }
        ?>
    </select>
    </p>
    </div>
        </div><?php
    }
add_action( 'woocommerce_product_data_panels', 'matching_product_tab_content' );

/**
 * Save meta
 */
function save_matching_product_tab_content( $post_id ) {
$product_field_type =  $_POST['product_field_type'];
    update_post_meta( $post_id, '_product_field_type_ids', $product_field_type );

}
add_action( 'woocommerce_process_product_meta_simple', 'save_matching_product_tab_content'  );
add_action( 'woocommerce_process_product_meta_variable', 'save_matching_product_tab_content'  );

Read more here: WooCommerce | update_post_meta doesn’t work