PHP Sessions: Start, Modify & Destroy Sessions

PHP Session is a mechanism to store information across multiple pages. Gain understanding on how to start, modify, & destroy PHP sessions using programming examples:

In this tutorial, you will learn what a PHP session is, how to start, modify, & destroy PHP sessions. Also, see the differences between cookies and sessions, and frequently asked questions (FAQs) related to this topic.

Please note that we have used PHP version 7 in all examples.

Let’s begin!

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PHP Sessions: The Ultimate Guide

What is a PHP Session

A PHP session is a technique to store and access information across multiple pages. Unlike cookies, sessions are stored on the server.

Sessions store information in variables, which are called PHP session variables. A normal variable can only be used within the page it was created. But a session variable can be created on one page and used on another.

Sessions are widely used on e-commerce websites where you need to store and pass cart details like product id, product name, product price, etc. from one page to another.

Uses of Sessions

Sessions are very useful in many ways. Some of the uses of sessions are:

• Track user activities.
• Disable multiple logins with the same user account.
• Limit the number of logins.
• Logouts a user automatically after a long period of inactivity.

How to Start a Session

A session can start anywhere on the page. The PHP session_start() function is used to start a session. The isset() function is used to check whether or not the session variable is set.

The superglobal, $_SESSION is used to store current PHP session variables.

The below example shows how to start a session.:

<?php
 
session_start();
 
if(isset( $_SESSION['visits'])){
    $_SESSION['visits'] += 1;
}else{
    $_SESSION['visits'] = 1;
}
 
echo "No. of visits in this session: ". $_SESSION['visits'];
 
?>

The following text shows the browser output of the above programming code:

• When you visit the web page for the first time:

No. of visits in this session: 1

• When you visit the web page for the second time:

No. of visits in this session: 2

Modifying a Session

Modifying a session is straightforward. You just need to overwrite the session variable.

Destroying a Session

In PHP, you have options to destroy either all session variables or a single session variable. The session_destroy() function destroys all session variables, while the unset() function unsets a single session variable.

• Destroy all session variables

<?php
 
session_destroy();
     
?>

• Unset a single session variable

<?php
 
unset($_SESSION['user']);
     
?>

The below example shows how to destroy a session:

<?php
 
session_start();
 
if(isset( $_SESSION['visits'])){
    $_SESSION['visits'] += 1;
}else{
    $_SESSION['visits'] = 1;
}
 
echo "No. of visits in this session: ". $_SESSION['visits'];
 
unset($_SESSION['visits']);
     
?>

The following text shows the browser output of the above programming code:

• When you visit the web page for the first time:

No. of visits in this session: 1

• When you visit the web page for the second time, third time…:

No. of visits in this session: 1

Cookies vs Sessions

The following table shows the differences between cookies and sessions:

Frequently Asked Questions

Conclusion

A session is a technique to store and access information across multiple pages. Unlike cookies, sessions are stored on the server. You can start, modify, and destroy PHP sessions.

The PHP session_start() function is used to start a session, while the session_destroy() and unset() functions are used to destroy sessions. To modify a session variable, you just need to overwrite the session variable.

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