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Home Backend Development PHP Tutorial php页面在同一浏览器打开不并发执行

php页面在同一浏览器打开不并发执行

Jun 06, 2016 pm 08:32 PM
php

遇到一个很奇葩的现象,test.php:(访问后隔10s打印时间)

<code><?php sleep(10);
echo date('Y-m-d H:i:s', time());
</code></code>
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同一个浏览器打开2个标签页,同时访问apache上的这个页面,为什么第2个页面永远会比第一个页面晚10s钟,在不同浏览器里同时打开就几乎同时输出。

难道是php处理同一浏览器的2个相同请求,不并发而是先后执行,这是为什么呢?

把apache换成nginx也是如此,这是php本来的特性还是哪设置的问题?

回复内容:

遇到一个很奇葩的现象,test.php:(访问后隔10s打印时间)

<code><?php sleep(10);
echo date('Y-m-d H:i:s', time());
</code></code>
Copy after login
Copy after login

同一个浏览器打开2个标签页,同时访问apache上的这个页面,为什么第2个页面永远会比第一个页面晚10s钟,在不同浏览器里同时打开就几乎同时输出。

难道是php处理同一浏览器的2个相同请求,不并发而是先后执行,这是为什么呢?

把apache换成nginx也是如此,这是php本来的特性还是哪设置的问题?

假设你只开启了1个PHP-FPM工作进程,PHP-FPM执行sleep(10)时会睡眠10秒,后面的请求必须等待10秒后才能被处理,不管是不同的标签页还是不同的浏览器。而且sleep调用比较特殊,就算浏览器按Esc中断请求,PHP-FPM也不会停止sleep。

不能同时返回应该是浏览器的机制,而不是PHP的问题,对同一个资源发出请求,如果第一个请求未响应,浏览器应该就不会发出第二个请求。如果第一个请求能及时响应,第二个请求也就能及时发出,比如同时访问下面的脚本,两个请求几乎是同时返回的,其中flush能及时响应,即使处理没有完成。

<code><?php ob_start();
echo date('H:i:s').'<br />';
echo str_repeat(' ', 1024*4);
ob_flush();
flush();
ob_end_flush();
sleep(10);
echo date('H:i:s');
</code>
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有可能是浏览器限制。某些浏览器是单线程。

@by快乐家园 所说的浏览器限制正对我的电脑 -- 也是chrome。
换做双开控制台,然后用两个curl去访问,结果就是几乎同时返回。

为什么会有浏览器限制呢,chrome应该是多进程的呀?
-- 初步猜测是因为cookie的问题,因为刚刚清掉所有cookie后,然后再访问就是同时返回了
为什么cookie会导致无法并行呢?
-- 检查下php的配置,发现session.auto_start = 1,修改为0,重启下服务器,再访问就同时返回了;
-- session会有锁,正是这个锁导致第一个请求结束后,第二个请求才真正开始。

原因可能有多方面,LZ可以检查下session.auto_start

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