


Regarding the problem of too many Session files in PHP,
PHP’s default mechanism: for every php request, there will be a 1/100 probability (default value) of triggering "session recycling" ". If "session recycling" occurs, the /tmp/sess_* files will be checked. If the last modification time exceeds 1440 seconds (the value of gc_maxlifetime), they will be deleted, which means that these sessions have expired
1. What is a session file
The file is generally /tmp/sessions/sess_4b1e384ad74619bd212e236e52a5a174If
username|s:9:"test";admin|s:1:"0";
2. When does session recycling occur?
By default, for every php request, there will be a 1/100 probability of recycling, so it may be simply understood as "one recycling occurs for every 100 php requests." This probability is controlled by the following parameters
#概率是gc_probability/gc_divisor session.gc_probability = 1 session.gc_divisor = 100
-
Assume that in this case gc_maxlifetime=120, if a session file was last modified 120 seconds ago, then the session will still be valid before the next recycling (1/100 probability) occurs.
-
If your session uses session.save_path to save the session elsewhere, the session recycling mechanism may not automatically process expired session files. At this time, you need to delete expired sessions manually (or crontab) regularly
3. Set the session storage directory
If you use php5-fpm, modify /etc/php5/fpm/php.ini
, modify or add the following line:
session.save_path = 3;600:/tmp/sessions
4. Session clearing script
#!/bin/sh find /tmp/php-session -cmin +24 -name "sess_*" -and -size 0 -delete > /dev/null 2>&1 find /tmp/php-session -cmin +1440 -name "sess_*" -delete > /dev/null 2>&1
We can get the time here through session.gc_maxlifetime, just put it in the scheduled task (crontab)
Other ways
-
Use memcache, etc., (session.save_handler = memcache)
-
Use cookies, but the cookies must be encrypted
5. Use tmfs to store session
1. Mount /tmp as tmpfs file system
Modify /etc/fstab and add the following content to the last line: /tmp/sessions tmpfs defaults,size=5120m 0 0
mount -a
2. Create session storage folder
php will not automatically create these folders, but some scripts for creating folders are provided in the source file. The script below is also easy to use. The content of the script is as follows
#!/bin/sh dir="0 1 2 3 4 5 6 7 8 9 a b c d e f" for levela in $dir; do for levelb in $dir; do for levelc in $dir; do mkdir -p /tmp/sessions/$levela/$levelb/$levelc; done done; done chown -R root:webgrp /tmp/sessions && chmod -R 1777 /tmp/sessions
Because /tmp/sessions is used for memory, all files in it will be lost after the server is restarted. Therefore, the above script needs to be added to /etc/rc.local and placed before starting php
3. Store sessions in different directories
php itself supports multi-level hashing of sessions. In php.ini, change ;session.save_path = /tmp to
session.save_path = "3;/tmp/sessions
4. Session recycling
Use the script above

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

在PHP中,可以利用implode()函数的第一个参数来设置没有分隔符,该函数的第一个参数用于规定数组元素之间放置的内容,默认是空字符串,也可将第一个参数设置为空,语法为“implode(数组)”或者“implode("",数组)”。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。


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