How to use Cookies and Sessions in PHP?

In Web development, Cookie and Session are two very commonly used concepts. They can help us save users' login status and other data to provide users with a better user experience. In PHP, it is also very convenient to use Cookie and Session. Let's introduce how to use Cookie and Session in PHP.

1. Use of Cookies

1. What is Cookie

Cookie, also known as "cookie", is a small piece of text stored on the user's computer by the web server. . When a user visits a web page, the web server will send the cookie to the user's computer and store it in the browser. Later, when the user visits the same website again, the browser will send the cookie back to the server, thereby achieving the purpose of passing data between the client and the server.

2. Set Cookie

To set Cookie, we can use the setcookie() function in PHP. The setcookie() function accepts three parameters: the name of the cookie, the value of the cookie, and the validity period of the cookie.

Sample code:

setcookie('name', 'John', time()+3600); //设置一个名为“name”的Cookie，值为“John”，有效期1个小时

In the above code, the first parameter is the name of the Cookie, the second parameter is the value of the Cookie, and the third parameter is the validity period of the Cookie. The parameter indicates that starting from the current time, the validity period of the cookie is 3600 seconds, which is 1 hour. If we want the cookie to be valid permanently, we can set the validity period to a large number, as shown below:

setcookie('name', 'John', time()+3600*24*365); //设置一个名为“name”的Cookie，值为“John”，有效期为1年

3. Read Cookie

To read the cookie, we can use PHP $_COOKIE global variable in. This variable is an associative array that contains all cookie names and values.

Sample code:

echo $_COOKIE['name']; //输出名为“name”的Cookie的值

In the above code, we use the echo statement to output the value of the cookie named "name".

4. Delete Cookie

To delete Cookie, we can use the setcookie() function and set the validity period to a past time point.

Sample code:

setcookie('name', '', time()-3600); //删除名为“name”的Cookie

In the above code, we set the validity period of the cookie to the current time minus 3600 seconds, which is the time point 1 hour ago, so that the cookie can be deleted .

2. Use of Session

1. What is Session

Session is a server-side data storage method that can be used to save the user's login status and other information. The use of Session is more secure than Cookie, because Session is stored on the server, while Cookie is stored on the user's computer.

2. Open Session

To open Session, we can use the session_start() function in PHP. This function will create a Session on the server and store a Cookie named "PHPSESSID" in the browser. The value of the Cookie is the ID of the Session.

Sample code:

session_start(); //开启Session

In the above code, we use the session_start() function to open the Session.

3. Set up Session

To set up Session, we only need to use the $_SESSION array after the session_start() function. The $_SESSION array is an associative array that can store any type of data.

Sample code:

$_SESSION['name'] = 'John'; //设置一个名为“name”的Session变量，值为“John”

In the above code, we use the $_SESSION array to set a Session variable named "name" with a value of "John".

4. Read Session

To read Session, we only need to use the $_SESSION array.

Sample code:

echo $_SESSION['name']; //输出名为“name”的Session变量的值

In the above code, we use the echo statement to output the value of the Session variable named "name".

5. Destroy Session

To destroy Session, we can use the session_destroy() function. This function will delete the Session on the server and delete the "PHPSESSID" cookie in the browser.

Sample code:

session_destroy(); //销毁Session

In the above code, we use the session_destroy() function to destroy the Session.

3. Comparison of Cookie and Session

Both Cookie and Session can be used to save the user's status and other information. The main difference between them is where the data is stored. Cookies are stored on the user's computer, while Sessions are stored on the server, so Sessions are more secure than Cookies. In addition, Session can store more data, while Cookie has a size limit.

To sum up, it is very convenient to use Cookie and Session in PHP. We only need to use a few simple functions and variables. When we need to save user status and other data, we can choose a data storage method that suits us.

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