//custom product tab to woocommerce edit
function sm_wccpd_custom_product_tabs($tabs)
{
    $tabs['sm_wcpa_extra_products'] = array(
        'label'  => __('Samanik Extra Products', 'sm-wcpa'),
        'target' => 'sm_wc_extra_products_options',
        'class'  => array('show_if_variable'),
    );
    return $tabs;
}

add_filter('woocommerce_product_data_tabs', 'sm_wccpd_custom_product_tabs');

function extra_products_options_product_tab_content()
{
    global $post;

    // Note the 'id' attribute needs to match the 'target' parameter set above
    ?>
    <div id='sm_wc_extra_products_options' class='panel woocommerce_options_panel'><?php
    ?>
    <div class='options_group'><?php
        woocommerce_wp_checkbox(
            [
                'id'    => '_has_extra_products',
                'label' => __('has extra products', 'sm-wcpa'),
            ]);
        woocommerce_wp_select(
            [
                'class'             => 'multiselect attribute_values wc-enhanced-select',
                'custom_attributes' => ['multiple' => 'multiple', 'style' => 'width:100% !importan;'],
                'id'                => '_sm_wcpa_product[]',
                'label'             => __('Extra Products to be add here', 'sm-wcpa'),
                'value'             => array_values(json_decode(get_post_meta($post->ID, '_sm_wcpa_product'), true)),
                'options'           => sm_wcpa_get_products_as_options(),//this is function that I pass Products as array like [product_id => product name]
            ]);

        ?></div>

    </div><?php
}

//  add_filter('woocommerce_product_data_tabs', 'extra_products_options_product_tab_content'); // WC 2.5 and below
    add_filter('woocommerce_product_data_panels', 'extra_products_options_product_tab_content'); // WC 2.6 and up