What is the difference between session and cookie in php?

The difference between session and cookie in php is: 1. Cookie is implemented by extending the http protocol, while session saves information in a form similar to a hash table; 2. Cookie is saved on the [client], The session is saved on the [server].

The difference between session and cookie in php is:

Specifically, the cookie is saved in the "Client" "end", and session is saved on the "server side"

1. cookie is implemented by extending the http protocol

Cookie mainly includes: name, value, expiration time, path and domain;

If the cookie does not set a life cycle, it will be closed when the browser is closed. This kind of cookie is generally stored in memory rather than on the hard disk. If On the contrary, setting a life cycle will not disappear when the browser is closed. These cookies will still be valid until the set expiration time is exceeded.

2. session Saves information in a hash table-like form.

When the program needs to create a session for a client's request, the server first checks the client Whether the client's request already contains a session identifier (called session id).

If it is included, it means that a session has been created for this client before. The server will retrieve this session according to the session id and use it (if it cannot be retrieved, it will create a new one). If the client request does not include the session id , then create a session for this client and generate a session id associated with this session. The value of the session id should be a string that is neither repeated nor easy to find patterns to counterfeit. This session id will be Return to the client for storage in this response.

The method of saving this session id can use cookies, so that during the interaction process, the browser can automatically send this identification to the server according to the rules. Generally, the name of this cookie is similar to SEEESIONID.

But cookies can be artificially prohibited, and there must be other mechanisms so that the session id can still be passed back to the server when cookies are prohibited.

Advantages and Disadvantages:

1. Cookie data is stored on the client's browser, and session data is placed on the server.

2. Cookies are not very safe. Others can analyze the COOKIE stored locally and deceive COOKIE

Considering security, session should be used.

3. The session will be saved on the server within a certain period of time. When access increases, it will take up more of your server's performance

In order to reduce server performance, COOKIE should be used.

4. The data saved by a single cookie cannot exceed 4K. Many browsers limit a site to save up to 20 cookies.

5. So personal suggestion:

Store important information such as login information as SESSION

If other information needs to be retained, it can be placed in COOKIE

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