Detailed explanation of session database storage instance in php

Although changing the Session storage folder prevents the Session from filling up the temporary folder and causing the site to crash, you can calculate that if a large website has 1,000 people logging in a day and 30,000 people logging in a month, then the site will There are 30,000 Session files. However, it is not easy to query a session_id in these 30,000 folders. At this time, it needs to be applied to session database storage, which is session_set_save_handle( in PHP )function. The syntax format is as follows:

session_set_save_handle(open, close, read, write, destroy,gc);

The parameter description of the session_set_save_handle() function is as follows:

Parameter	Description
open(save_path, session_name)	Find the Session storage address and take out the variable name
close()	No parameters required, close the database
read(key)	Read the Session key value, key corresponds to session_id
write(key, data)	data corresponds to the set Session variable
destroy(key)	Log out the session corresponding to the Session key value
gc(expiry_time)	Clear expired Session records

General The application parameters use variables directly, but the parameters in this function are 6 functions, and when called, only the string of the function name is called. These parameters will be introduced separately below, and finally these functions will be encapsulated into a class.

(1) Encapsulate the session_open() function to connect to the database. The code format is as follows:

<?php
  function session_open($save_path,$session_name)
  {
     //连接 mysql 数据库
     $handle = mysqli_connect(&#39;localhost&#39;,&#39;root&#39;,&#39;root&#39;,&#39;db_test&#39;);
     // 判断数据库是否成功
     if(!$handle)
     {
        die(&#39;打开数据库失败&#39;);
     }
  }
?>

Description: In the above code, $save_path and $session_name are two The two parameters are not used. You can remove these two parameters here, but generally it is recommended that friends keep the two parameters entered, because these two variables are generally used.

(2) Encapsulate the session_close() function to close the database connection. The code format is as follows:

<?php
  function session_close()
  {
     $handle = mysqli_connect(&#39;localhost&#39;,&#39;root&#39;,&#39;root&#39;,&#39;db_test&#39;);
     mysqli_close($handle);
     return(true);
  }
?>

Description: No parameters are required in this function , so whether the Session is stored in a database or a file, you only need to return true. But if it is a MYSQL database, it is best to close the database to ensure that there will be no trouble in the future.

(3) Encapsulate the session_read() function, set the UNIX timestamp of the current time in the function, and search the Session name and content based on the $key value. The example code is as follows:

<?php
  function session_read($key)
  {
     //连接数据库
     $handle = mysqli_connect(&#39;localhost&#39;,&#39;root&#39;,&#39;root&#39;,&#39;db_test&#39;);
     //设定当前时间
     $time = time();
     $sql = "select session_date from tb_session where session_key=&#39;$key&#39;and session_time>$time ";
     $result = mysqli_query($handle,$sql);
     $row = mysqli_fetch_array($result);
     if($row)
     {   //返回 Session 名称和内容
        return($row[&#39;session_date&#39;]);
     }else{
        return(false);
     }
  }
?>

Explains that the session_expiry stored in the database is a UNIX timestamp.

(4) Encapsulation session_write() function, the Session expiration time is set in the function, and the Session name and content are searched. If the query result is empty, the Session in the current page will be inserted into the database based on session_id, session_name, and expiration time; if the query result is not empty, the Session storage information in the database will be modified based on $key and the execution result will be returned. The example code is as follows:

<?php
  function session_write($key,$data)
  {
     //连接数据库
     $handle = mysqli_connect(&#39;localhost&#39;,&#39;root&#39;,&#39;root&#39;,&#39;db_test&#39;);
     //设定失效时间
     $time = 60*60;
     // 得到 UNIX 时间戳
     $lapse_time = time() + $time;
     $sql = "select session_date from tb_session where session_key=&#39;$key&#39;and session_time>$lapse_time ";
     $result = mysqli_query($handle,$sql);
     if(mysqli_num_rows($result) == 0)  // 没有结果
     {    //插入数据库SQL语句
        $sql = "insert into tb_session values (&#39;$key&#39;,&#39;$data&#39;,$lapse_time)";
        $result = mysqli_query($handle,$sql);
     }else{
        // 修改数据库SQL语句
        $sql = "update tb_session set session_key=&#39;$key&#39;, sessoin_data=&#39;$data&#39;, session_time=$lapse_time where session_key=&#39;$key&#39; ";
        $result = mysqli_query($handle,$sql);
     }
     return($result);
  }
?>

(5) Encapsulate the session_destroy() function to delete the Session in the database according to the $key value. The code is as follows:

<?php
  function session_destroy($key)
  {
     //连接数据库
     $handle = mysqli_connect(&#39;localhost&#39;,&#39;root&#39;,&#39;root&#39;,&#39;db_test&#39;);
     // 删除 Session 的 SQL 语句
     $sql = "delete from tb_session where session_key=&#39;$key&#39;";
     $result = mysqli_query($handle,$sql);
     return($result);
  }
?>

(6) Encapsulate the session_gc() function and delete the expired Session according to the given expiration time. The code is shown as follows:

<?php
  function session_gc($expiry_time)
  {
     //连接数据库
     $handle = mysqli_connect(&#39;localhost&#39;,&#39;root&#39;,&#39;root&#39;,&#39;db_test&#39;);
     // 将参数$expiry_time 赋值为当前时间戳
     $lapse_time = time();
     // 删除 Session 的 SQL 语句
     $sql = "delete from tb_session where expiry_time<$lapse_time";
     $result = mysqli_query($handle,$sql);
     return($result);
  }
?>

The above are the 6 parameters (functions) of the session_set_save_handler() function. .

The following uses the function session_set_save_handler() to implement the Session storage database. The implementation code is as follows:

<?php session_set_save_handler(&#39;session_open&#39;,&#39;session_close&#39;,&#39;session_read&#39;,&#39;session_write&#39;,&#39;session_destroy&#39;,&#39;session_gc&#39;);
  session_start();
  // 下面为我们定义的 Session
  $_SESSION[&#39;user&#39;] = &#39;tom&#39;;
  $_SESSION[&#39;pwd&#39;] = &#39;12345&#39;;
?>

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