什么会导致双页请求? [英] What can cause a double page request?

问题描述

我目前正在调查我网站上的重复请求问题.并不是所有的时间，但有时，请求的页面实际上会加载两次……这实际上不是问题，直到它位于带有PHP的页面上，该页面根据请求(我的跟踪脚本)将内容插入到我的数据库中.

I am currently investigating a double request problem on my site. Not all the time, but sometimes, a requested page will in fact load twice...which is not a problem really until it is on a page with PHP that inserts stuff into my db on request (my tracking script).

我已经阅读到图像标签中的src为空，而CSS背景中的url()为空可能会导致该页面被请求两次.

I have read that an empty src in an image tag, and an empty url() in a css background could potentially cause the page to be requested twice.

但是，我找不到任何问题.

However, I can't find any problems with those.

还有其他可能导致这种情况的原因吗?

Is there anything else that could be causing something like this?

回答我的情况

经过大量研究，结果证明，就我而言，第二个请求来自用户代理"Mediapartner-Google".我开始注意到，在放有Adsense广告的网页上，我自己访问网页后的几秒钟内，就会期望该抓取工具进行二次访问.

After some extensive research, it turns out that in my case specifically, the second request has been coming from the user agent "Mediapartner-Google". I began to notice that on pages that serve an Adsense ad, I could expect a secondary visit from this crawler within seconds after I visit the page myself.

在没有Adsense广告的网页上似乎不会发生这种情况.

This doesn't seem to be happening on pages without Adsense ads.

我将在下面标记一个答案，因为在大多数情况下，这些都是需要检查的正确内容.

I am going to mark an answer below, because it seems like for most situations, those are the correct things to check.

推荐答案

我以前见过的原因:

• 缺少样式表或图像

• Missing stylesheet or image

如果您要验证HTML等，则Chrome/Firefox的Web开发人员插件有时会请求两次.

Web developer addon for Chrome/Firefox sometimes requests things twice if you're validating HTML etc.

有时候很难找到重复请求的根本原因.

Sometimes it's just too difficult to track down the root cause of a double request.

无论哪种方式，您都应该不通过GET请求更改数据库状态(或会话状态).您应该在没有postdata的情况下运行的唯一SQL查询是SELECT.即使表单仅包含一个提交按钮，也应使用表单来完成所有更新和插入.

Either way, you should NOT be changing database state (or session state) through a GET request. The only SQL query you should be running without postdata is SELECT. All updates and inserts should be done using forms, even if the form consists only of a submit button.

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