How to register and read Session in php

Register Session

Using Session Variables in php, in addition to starting, you also need to go through a registration The process of registering and reading Session variables must be completed by accessing the $_SESSION array. Starting from PHP 4.1.0 version, $_SESSION becomes a super global array like $_POST, $_GET and $_COOKIE, etc., but it can only be used after calling session_start() Function to open the Session. Unlike $HTTP_SESSION_VARS, $_SESSION always has global scope, so do not use the global keyword with $_SESSION. Key names in the $_SESSION associative array have the same naming rules as ordinary variable names in PHP.

After session variables are created, they are all stored in the array $_SESSION. Creating a session variable from the array $_SESSION is easy, just add an element directly to the array.

For example, the following example will start the session, create a Session variable and assign it a null value. The code is as follows:

<?php
  session_start();                                       // 启动 Session
  $_SESSION[&#39;name&#39;] = null;                   // 声明一个名为 admin 的变量，并设置为空值 null。
?>

After executing the script, the Session variable will be saved somewhere on the server side. in a folder. The location of the file is changed through the php.ini file. In the directory specified by the session.save_path attribute, a separate file is created for this access user to save the registered Session variables. For example, the name of a file that saves Session variables is in the form of "sess_09403850rf7sk39s67". The file name contains the Session ID, so each access user has his own file that saves Session variables in the server, and this file can be directly Use a text editor to open. The content structure of the file is as follows:

Variable name | Type: Length: Value             //The same structure applies to each variable to save

As mentioned above, let’s give a simple example:

<?php
  //启动 session
   session_start();
  //注册 session 变量，赋值为一个用户名称
  $_SESSION[&#39;usermane&#39;] = "sky";
  //注册 session 变量，赋值为一个用户id
  $_SESSION[&#39;uid&#39;] = 1;
?>

In the above example, Session has registered two variables. If a file that saves Session variables for this user is found in the server, , after opening, you can see the following content:

username | s:6: "sky"; uid | i:1:"1"; The contents of the two variables

Read the Session

First you need to determine the session variables Whether a session ID exists, if not, create one and make it accessible through the global array $_SESSION; if it already exists, load the created session variable for use by the user.

For example: Determine whether the Session variable storing the user name is empty. If not, assign the session variable to $my_value.

The code is shown as follows:

<?php
  if(!empty($_SESSION[&#39;session_name&#39;])){       //判断存储用户名的  Session 会话变量是否为空
    $my_value = $_SESSION[&#39;session_name&#39;];     //将会话变量赋予一个变量 $my_value
  }
?>

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