How to use session in php

For details on how to use php session, see: php session session topic

* session session

* session is very similar to cookie, It just saves the user data to the page on the server

* But the query key is still on the browser, saved with a special cookie

* This special key is called: PHPSESSID( Session ID)

//The session must be opened before all html code is output to the browser

//session_start() will send a 32-bit hexadecimal PHPSESSID# to the browser

##//There must be no statements such as echo, print, include, or even blank lines before opening a session

//Once the session is opened successfully, we can save the user's session information On the server

//All operations of the session are implemented through the super global variable $_SESSION

//Tmp/php/32-bit text file corresponding to PHPSESSID on the server

//user_name|s:5:"admin";user_id|i:1;

//Syntax: variable name|type: value; use a semicolon between each session variable separated, the string type will have a length prompt

//Session access is very similar to cookies, use the $_SESSION array directly

//Update

//Delete

//1. Delete a single session variable

//2. Delete all session variables and clear the contents of the session file on the server

//3. Clear For all user sessions, delete the session files on the server

//If you want to completely delete the session, the cookie corresponding to the PHPSESSID on the browser should also be deleted

//Execute , there can be no more setting statements in front, otherwise a PHPSESSID will be regenerated

//Summary: Correct and safe deletion of session should include the following three steps: