What is a session in PHP?

A session in PHP is used to maintain state and store information for a user across multiple pages of a web application. When a session is initiated, PHP starts a session and generates a unique session ID for each user. This ID is usually stored in a cookie on the user's browser or passed via URL, allowing the server to identify the session for subsequent requests. During the life of the session, various types of data—such as user preferences, authentication details, or shopping cart contents—can be stored in a session variable which users can access as they navigate through different pages.

This functionality is essential for building user experiences that rely on persistent information, such as keeping users logged in or retaining selected items in a shopping cart while they browse the site.

While storing information on the server is part of how sessions work, this description doesn't fully capture the broader functionality of sessions managing state and continuity across multiple pages. Techniques for submitting forms and running multiple scripts also do not relate directly to the concept of sessions, as they refer to different aspects of web application behavior and functionality.