Detailed explanation of the method of storing sessions in php into redis or memcache

Introduction to Session

session, often translated as conversation in Chinese, its original meaning refers to a series of actions/messages that have a beginning and an end, such as from picking up the phone to dialing to hanging up when making a phone call. The series of processes in the middle can be called a session. Sometimes we can see words like "During a browser session,..." The word session here is used in its original meaning, which refers to the period from the opening to closing of a browser window①. The most confusing thing is the sentence "the user (client) during a session", which may refer to a series of actions of the user (generally a series of actions related to a specific purpose, such as from logging in to purchasing goods). The online shopping process from checkout to logout is sometimes called a transaction). However, sometimes it may just refer to a connection, or it may refer to meaning ①. The difference can only be inferred from the context ②.

However, when the word session is associated with a network protocol, it often implies two meanings: "connection-oriented" and/or "maintaining state". "Connection-oriented" refers to the communication between both parties. Before communicating, you must first establish a communication channel, such as making a phone call. Communication cannot begin until the other party answers the phone. In contrast, when you send a letter, you cannot confirm whether the other party's address is correct. The communication channel may not be established, but for the sender, the communication has already begun. "Maintaining status" means that the communicating party can associate a series of messages so that the messages can depend on each other. For example, a waiter can recognize an old customer who comes again and remember that the customer owed the store a dollar last time. . Examples of this category include "a TCP session" or "a POP3 session" ③.

In the era of vigorous development of web servers, the semantics of session in the context of web development have been expanded. Its meaning refers to a type of information used to maintain state between the client and the server. Solution ④. Sometimes session is also used to refer to the storage structure of this solution, such as "Save xxx in session"⑤. Since various languages ​​used for web development provide support for this solution to a certain extent, session is also used to refer to the solution of that language in the context of a specific language, such as often The javax.servlet.http.HttpSession provided in Java is referred to as session⑥.

Since this confusion is irreversible, the use of the word session in this article will also have different meanings depending on the context. Please pay attention to the distinction.
In this article, the Chinese "browser session period" is used to express the meaning ①, the "session mechanism" is used to express the meaning ④, the "session" is used to express the meaning ⑤, and the specific "HttpSession" is used to express the meaning ⑥

Why should SESSION be saved in the cache?

As far as PHP is concerned, the session supported by the language itself is saved to a disk file in the form of a file, and is saved in the specified In the folder, the saved path can be set in the configuration file or using the function session_save_path() in the program. However, there are disadvantages to doing so.

The first is to save to the file system, which is inefficient. As long as the session is used, the specified sessionid will be searched from multiple files, which is very inefficient.

The second is that when multiple servers are used, the problem of session loss may occur (actually it is saved on other servers).

Of course, saving in the cache can solve the above problem. If you use PHP's own session function, you can use the session_set_save_handler() function to easily re-control the session processing process. If you don't use PHP's session series functions, you can write a similar session function yourself, which is also possible. This is the project I'm working on now. It will calculate the hash as the sessionId based on the user's mid and login time. Each time it is requested, The sessionId must be added to be legal (it is not needed when logging in for the first time, the sessionId will be created at this time and returned to the client). This is also very convenient, concise and efficient. Of course, what I am mainly talking about in this article is "manipulating things" in PHP's own SESSION.

SESSION is saved in the cache

php saves the cache to Redis. You can use the configuration file to modify the processing and saving of the session. Of course, in the program You can also use the ini_set() function to modify it. This is very convenient for testing. I will use this method here. Of course, if it is a production environment, it is recommended to use the configuration file.

If you want to simply operate the session into redis, you can run the following code

<?php
ini_set("session.save_handler", "redis");
ini_set("session.save_path", "tcp://localhost:6379");
session_start();
header("Content-type:text/html;charset=utf-8");
$_SESSION[&#39;view&#39;] = &#39;zhangsan&#39;;
echo $_SESSION[&#39;view&#39;];

Here, set the session.save_handler mode to redis, and session.save_path to the address and port of redis. Refresh after setting. If you look back at redis, you will find that the sessionId is generated in redis. The sessionId is the same as the one requested by the browser.

If it is memcache

<?php
ini_set("session.save_handler", "memcache");
ini_set("session.save_path", "tcp://localhost:11211");
session_start();
header("Content-type:text/html;charset=utf-8");
$_SESSION[&#39;view&#39;] = &#39;zhangsan&#39;;
echo $_SESSION[&#39;view&#39;];

, you can also use

Session_set_save_handler(‘open’,’close’,’ read’,’ write’,’ destory’,’ gc’);

The usage is as follows: Customize a Redis_session class

<?php
class RedisSession{
    private $_redis = array(
        &#39;handler&#39; => null, //数据库连接句柄
        &#39;host&#39; => null,   //redis端口号
        &#39;port&#39; => null,
    );
    public function __construct($array = array()){
        isset($array[&#39;host&#39;])?$array[&#39;host&#39;]:"false";
        isset($array[&#39;port&#39;])?$array[&#39;host&#39;]:"false";
        $this->_redis = array_merge($this->_redis, $array);
    }
    public function begin(){
        //设置session处理函数
        session_set_save_handler(
            array($this, &#39;open&#39;),
            array($this, &#39;close&#39;),
            array($this, &#39;read&#39;),
            array($this, &#39;write&#39;),
            array($this, &#39;destory&#39;),
            array($this, &#39;gc&#39;)
        );
    }
    public function open(){
        $redis = new Redis();
        $redis->connect($this->_redis[&#39;host&#39;], $this->_redis[&#39;port&#39;]);
        if(!$redis){
            return false;
        }
 
        $this->_redis[&#39;handler&#39;] = $redis;
        $this->gc(null);
        return true;
    }
    //关
    public function close(){
        return $this->_redis[&#39;handler&#39;]->close();
    }
    //读
    public function read($session_id){
        return $this->_redis[&#39;handler&#39;]->get($session_id);
    }
    //写
    public function write($sessionId, $sessionData){
        return $this->_redis[&#39;handler&#39;]->set($sessionId, $sessionData);
    }
    public function destory($sessionId){
        return $this->_redis[&#39;handler&#39;]->delete($sessionId) >= 1 ? true : false;
    }
    public function gc(){
        //获取所有sessionid，让过期的释放掉
        $this->_redis[&#39;handler&#39;]->keys("*");
        return true;
    }
}
$ses = new RedisSession(array(&#39;host&#39;=>&#39;127.0.0.1&#39;,&#39;port&#39;=>&#39;6379&#39;));
$ses->begin();
session_start();
$_SESSION[&#39;name&#39;]=&#39;zhangsan&#39;;
echo $_SESSION[&#39;name&#39;];

In this way, session data such as redis must be installed during the execution of the redis code

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