足球游戏_中国足彩网￥体育资讯$

PHP session过期机制和配置/session回收

Posted by feng on 2010/05/11 Leave a comment (0)Go to comments

使用PHP session时会遇到明明超过了session过期时间，但session依然完好无损的活着，让人头大。其实仔细看一下php.ini关于PHP session回收机制就一目了然了。

session 回收机制：

PHP采用Garbage Collection process对过期session进行回收，然而并不是每次session建立时，都能够唤起 ‘garbage collection’ process ，gc是按照一定概率启动的。这主要是出于对服务器性能方面的考虑，每个session都触发gc，浏览量大的话，服务器吃不消，然而按照一定概率开启 gc，当流览量大的时候，session过期机制能够正常运行，而且服务器效率得到节省。细节应该都是多年的经验积累得出的。

三个与PHP session过期相关的参数(php.ini中)：

session.gc_probability = 1

session.gc_divisor = 1000

session.gc_maxlifetime = 1440

gc启动概率 = gc_probability / gc_divisor = 0.1%

session过期时间 gc_maxlifetime 单位：秒

建议：

自己测试时，当然把这个session过期概率设置越大越好，过期效果才明显。

当web服务正式提供时，session过期概率就需要根据web服务的浏览量和服务器的性能来综合考虑session过期概率。为每个 session都开启gc，显然是很不明智的。

变通方法：

手动在代码中为session设定上次访问时间，并且每次访问的时候判断访问间隔是否超过时间限制，超过手动销毁session，未超过则更新上次 访问时间。这种方法还可以限制两次访问间隔。

配置文件摘录（来自php.ini），英文的原汁儿原味儿

; Defines the probability that the ‘garbage collection’ process is started

; on every session initialization. The probability is calculated by using

; gc_probability/gc_divisor. Where session.gc_probability is the numerator

; and gc_divisor is the denominator in the equation. Setting this value to 1

; when the session.gc_divisor value is 100 will give you approximately a 1% chance

; the gc will run on any give request.

; Default Value: 1

; Development Value: 1

; Production Value: 1

; http://php.net/session.gc-probability

session.gc_probability = 1

; Defines the probability that the ‘garbage collection’ process is started on every

; session initialization. The probability is calculated by using the following equation:

; gc_probability/gc_divisor. Where session.gc_probability is the numerator and

; session.gc_divisor is the denominator in the equation. Setting this value to 1

; when the session.gc_divisor value is 100 will give you approximately a 1% chance

; the gc will run on any give request. Increasing this value to 1000 will give you

; a 0.1% chance the gc will run on any give request. For high volume production servers,

; this is a more efficient approach.

; Default Value: 100

; Development Value: 1000

; Production Value: 1000

; http://php.net/session.gc-divisor

session.gc_divisor = 1000

; After this number of seconds, stored data will be seen as ‘garbage’ and

; cleaned up by the garbage collection process.

; http://php.net/session.gc-maxlifetime

session.gc_maxlifetime = 1440

中国足彩网信息请查看IT技术专栏