购买指定商品赠送用户会员，

/*购买指定商品赠送会员*/
function zb_api_pay_success($pay_order)
{
    $pay_order = (array) $pay_order;
    $post_id   = $pay_order['post_id'];
    $user_id   = $pay_order['user_id'];

    $vip_time  = date('Y-m-d H:i', strtotime('+1 month'));

    if ($user_id && $post_id && $post_id == 1347) {
        update_user_meta($user_id, 'vip_exp_date', $vip_time);
        update_user_meta($user_id, 'vip_level', 1);
    }
}
add_action('payment_order_success', 'zb_api_pay_success');