AH Computing Science - Web Development - Lesson 6: PHP sessions

For the Scottish Advanced Higher Computing course.
Explanation of PHP sessions.

A PHP session is a way of storing information to be used across multiple pages of a single website.
Information can be stored in session variables (which are stored on the server) which can be accessed across different pages.
Session variables are stored on the server until the browser tab is closed or there are 30 minutes of inactivity (this is configurable).v

Example 1 - Logging in to a secure site
A user types their username and password into a form and clicks the submit button.
Their login details are checked against those stored in the database.
If the user logs in successfully a session is started.
Their user id is stored in a session variable.
Every page they visit includes the session_start() command. This means that, for the duration of their visit to the site, every page has access to their user id (and therefore the rest of their details).
When the user leaves the site the session on the server is destroyed. Alternatively, if the user clicks the log out button, the session_destroy() command is executed.

Example 2 – Shopping as a guest
A user is browsing a shopping site as a guest (i.e. they are not logged in).
Every page they visit includes the session_start() command.
Their basket is stored in a session variable.
This means that, for the duration of their visit to the site, every page has access to their basket. If they update their basket, the session variable is updated.
When the user leaves the site the session on the server is destroyed.