Learn HTTP responses in PHP: headers, status codes, and cookies

In Web development, the HTTP protocol is the most widely used protocol. Learning the HTTP response part in PHP, including headers, status codes and cookies, will help developers better understand the website's access mechanism and improve the website's response speed and security.

Headers in HTTP response

HTTP response header refers to some metadata returned by the server when responding to the browser request. These metadata contain information about the response, such as the server's Type, response data type, response time, etc. The metadata of the HTTP response header consists of a key-value pair, each pair of key-value pairs is separated by a colon, and the key-value pairs are separated by carriage returns and line feeds.

In PHP, we can use the header() function to set the response header. For example, we can add a cacheable Expires header to the web page:

header("Expires: ".gmdate('D, d M Y H:i:s', time() + 3600) . ' GMT');

The above code will set the Expires in the response header to be cached for 1 hour.

HTTP status code

The HTTP status code is a three-digit code used to convey information about the processing results of the HTTP response. Common status codes are:

• 200 OK: The client request is successful.
• 301 Moved Permanently: The requested resource has been permanently moved to a new URL.
• 403 Forbidden: The server denies the access request.
• 404 Not Found: The server cannot find the requested resource.
• 500 Internal Server Error: The server encountered an unpredictable error.

In PHP, we can use the header() function to set the status code.

For example, we can set a 404 status code to indicate that the requested resource does not exist:

header("HTTP/1.1 404 Not Found");

This status code will be displayed in the response as:

HTTP/1.1 404 Not Found

Cookie

Cookies are small files stored on the client computer by the web server to store session information, user preferences, etc. Through cookies, web servers can share data between multiple pages, thereby improving the user's website access experience.

In PHP, we can use the setcookie() function to create and manage Cookies. For example, we can create a cookie with the name username, value John Doe, and a validity period of 1 hour:

setcookie("username", "John Doe", time()+3600);

The above code will create a cookie with the name username, value John Doe, and Cookies valid for 1 hour.

In the next visit, we can obtain and manage Cookies through the $_COOKIE array. For example, we can get the cookie named username through the following code:

$username = $_COOKIE['username'];

Through the above code, we can get the previously set cookie named username to proceed to the next step.

Summary

The headers, status codes and cookies in the HTTP response are a very important part of the web development process. Correctly setting response headers, status codes and cookies can improve the response speed and security of the website, thereby improving user experience. Learning HTTP responses in PHP will help us better understand these mechanisms and further optimize our web development work.

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