What is the difference between session and cookie in PHP?

Session and cookie are two commonly used technologies in web development for storing and transferring data between the server and client. The following outlines their differences:

1. Storage location: Cookies are stored on the client’s browser, while session data is stored on the server.
2. Security: Cookies are relatively insecure because their data can be modified and tampered with by the client, whereas session data is stored on the server-side and cannot be directly modified by the client.
3. Storage Capacity: Cookies are stored on the client side, so their storage capacity is limited by the browser, typically around 4KB. In contrast, session data is stored on the server side, allowing for the storage of larger amounts of data.
4. Lifecycle: Cookies can be set with an expiration time to remain valid for a certain period, or they can expire once the browser is closed. Sessions, on the other hand, will typically expire once the user closes the browser, but an expiration time can be set to keep the session active for a specific period.
5. Transmission method of data: Cookies data is sent to the server on every HTTP request, leading to an increase in the amount of data being transmitted over the network. On the other hand, session data is only stored on the server side, with only one session ID being sent to the server on each request.
6. Scenarios: Cookies are used in situations where state information needs to be maintained on the client side, such as remembering a user’s login status. Whereas sessions are used in cases where state information needs to be maintained on the server side, such as storing shopping cart data.

Depending on the specific requirements, you need to choose whether to use cookies or sessions.