PHP sessions are used to store data about a user between different requests. They allow developers to store user-specific data on the server-side, which can be accessed across multiple pages or requests. Sessions start when a user logs in to a website and end when the user logs out or when the session times out.
Sessions work by assigning a unique session ID to each user. This session ID is then stored as a cookie on the user’s computer, or it can be passed between pages using a URL parameter. When a user accesses a page, PHP checks if there is a session ID in the cookie or URL parameter. If there is, PHP retrieves the session data from the server and loads it into the session variables. If there isn’t, PHP creates a new session ID and starts a new session.
Session data is stored on the server-side, typically in a temporary folder. Developers can store any type of data in session variables, including strings, arrays, objects, and resources. The session data is only accessible to the user who created the session, making it a secure way to store user-specific data.
Session variables are accessed using the
$_SESSION superglobal array. To store data in a session variable, developers simply set a key-value pair in the
$_SESSION array. For example:
$_SESSION['username'] = 'johndoe';
To retrieve data from a session variable, developers can access it like any other array. For example:
echo 'Welcome, ' . $_SESSION['username'];
In summary, PHP sessions are a powerful feature that allows developers to store user-specific data on the server-side. They are commonly used for tasks such as user authentication, shopping carts, and personalized content. Understanding how to use sessions is an important skill for any PHP developer.