What are sessions in PHP?

• The session is a superglobal variable and it is an alternative way to store data across multiple pages or it preserve data across subsequent HTTP requests.
• The session can be defined as a method to store information on the server, which can be used in the future.
• When you work with a web server, the webserver don't know who you are, when you last work with it, what you do, etc. That means the HTTP address does not maintain the address.
• The session introduces a problem for this problem by storing information across multiple pages.
• If you set a session value to a variable, it can be used across multiple pages.
• The session variable holds the information in one variable and it can be used all the web pages of the same application until the session is destroyed.
• Session and Cookies are used to store user information.
• Sessions are stored in the server-side machine, whereas cookies are stored in a client-side machine.
• For example when a user login to the server, a session will create in the webserver.

Start a session in PHP

   <?php
     session_start();
   ?>

Create a session variable

• Syntax:

  $_SESSION[variable_name] = $value;

• Example:

  $_SESSION['user_name'] = "Ashok";

Get the session variable

  <?php
   echo $_SESSION['user_name'];
  ?> 

To show all the session variable

   print_r($_SESSION);

To destroy a session

    //To destroy a single variable
    unset($_SESSION['user_name']);

    //To remove all the session variables
    session_unset();

    //To destroy the session
    session_destroy();