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PHP中精准高速的UA识别

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Jun 13, 2016 pm 01:04 PM

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PHP中精准快速的UA识别

UA：user-agent 这在PHP提供的服务器变量中就能得到。user-agent 识别的目的是什么？

1、是什么浏览器？这已不需要了。CSS的HACK可以帮助你按浏览器正确渲染。

2、浏览器类型：这是肯定要的，我们最想要的，就是了解它是PC机中的，还是手机中的，这样，我们可以选择不同的页面。

3、user-agent：表面上是与浏览器类型是同一概念，实际是不一样的。user-agent的范围要比浏览器类型更广。因为，来访者不仅有浏览器类，同时还有应用程序，搜索机器人，以及垃圾网站前来抓取信息的。对于垃圾网站前来抓取信息的，当然，很多是伪装的，对付它，那不在UA识别中处理，而是在IP路由中处理的事情了。

MVC模式中的UA路由，最主要是要让客户端请求，最终显示对应的正确的页面。

但PHP中没有很好的函数，或可扩展，可维护的第三方开源，能够真正快速进行UA识别。

get_browser函数，虽说是C语言级别的，但它的相关的INI文件却要实时下载，并且，好几百K的一个INI大文件，在其中搜索正确的UA，然后，再根据不同的算法算出对应的结果，效率快时，当然好，一旦下载网速不行，或进程太多，机器内存紧长，速度马上直线下降。这不能不说是一个悲剧。

最好的做法，是将现在所有的UA字串，完全拆分出来，我们就会发现，一些字串，肯定是ROBOT专有，一些字串，肯定是MOBILE专有。由此，做成一个CSV，那么，现在这样的数据，只是两个字段的不足1000条记录的文件了。于是文件大小也只是降到了20KB以内。要处理的数据缩小了25倍左右。速度比原来的最快速度加快20倍，比原来的最慢速度加快200倍以上了。

为什么呢？想想1000条记录，折半查找，需要几次找完？并且，在20KB文本中折半查找不到1000行的记录，肯定远比在400多K的文件当中查找不可折半查找的2万多行的配置记录要快多了。

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