我可以尝试为您提供以下解决方案:当用户 A 将电子邮件发送给用户 B 时，您将其保存在表中，例如surveys_send，并带有随机生成的唯一代码.当用户 B 访问来自用户 A 的链接时，它看起来像survey.php?randomcode=12345 并且随机码是发送电子邮件时生成的唯一代码.当用户输入此调查脚本时，它会检查并向用户 A 发送有人访问了此 URL 的响应.

I can try to provide you solution below: When user A send the email to user B you save it in table like surveys_send with an unique code that will be randomly generate. When user B visits the link from user A it can look something like survey.php?randomcode=12345 and randomcode is this unique generated code when sending the email. When the user enters this survey script it will check and send an response to user A that someone visited this url.