PHP

Programming language

PHP has been the mainstay of many web applications for over two decades. Therefore, it is not surprising that methods and techniques have evolved to handle the intricacies of web communication, including HTTP status codes.

The Importance of HTTP Status Codes

Before delving deeper into PHP, it is important to clarify the purpose and significance of HTTP status codes. They are essential for communication between web servers and browsers, as they provide information about the outcome of a request.

There are several classes of status codes:

2xx (Success): Indicates that the request was successfully processed.
3xx (Redirection): Indicates that further actions need to be taken to complete the request.
4xx (Client Error): These codes indicate that there is a problem with the request, often due to a user error.
5xx (Server Error): In this case, the server has recognized that it made an error or is unable to fulfill the request for some reason.

PHP and Status Codes: A Historical Overview

In the early days of PHP, long before the frameworks and extensive libraries we know today, developers had to rely on the most basic language functions to set HTTP status codes. The header() function played a central role in this process.

The header() function allows sending raw HTTP headers. Setting status codes looked like this:

header('HTTP/1.0 404 Not Found‘);

Another common status code that was manually set is the 301 redirection code, often used for SEO purposes:

header('HTTP/1.0 301 Moved Permanently‘);
header('Location: /new-url.php‘);

However, this approach had several disadvantages:

Susceptible to errors: A missing space or...
Complexity: Developers had to memorize or look up the exact HTTP string for each status code.
Inconsistency: Different servers or PHP configurations could behave differently if the headers were not formatted exactly right.

The Evolution: Introducing the http_response_code() Function

Over time and with the advancement of the PHP engine, the PHP community recognized the need to simplify and make this process less error-prone. This led to the introduction of the http_response_code() function.

This function allows setting the HTTP status code simply by providing the numerical code:

http_response_code(404);

The benefits of this method are clear:

Simplicity: It is much more intuitive and less prone to human errors.
Flexibility: Developers no longer need to worry about the exact HTTP protocol version or the precise text of the status message; PHP handles it internally.
Readability: The code becomes cleaner and easier to understand, especially for developers who are new to a project or have less experience with HTTP status codes.

Additional Assistance in Modern PHP

While http_response_code() represents a significant improvement, many modern PHP frameworks and libraries have introduced their own tools and methods for handling HTTP status codes. These often provide even higher levels of abstraction and additional helper functions.

For example, in the Laravel framework:

return response('Not Found', 404);

Or in the Symfony framework:

return new Response('Not Found', 404);

These modern frameworks and their methods offer even greater consistency, improved testing capabilities, and tighter integration with other parts of the web application.

In summary, PHP has undergone a remarkable evolution over the years: from error-prone and manual techniques for setting HTTP status codes to the currently much more intuitive and robust methods.

Best Practices

Keep logic clear: Ensure that the logic used to send status codes is clear and easily understandable. Avoid deeply nested conditions that could lead to multiple possible status codes.
Avoid magic: Do not rely on frameworks or libraries to automatically set status codes unless you understand exactly how and why they do so.
Documentation: Maintain internal documentation explaining when and why certain status codes are sent.

Common Issues and Solutions

Headers already sent: This error occurs when attempting to send a header or status code after output content has already been sent. The solution is to ensure that all calls to header() or http_response_code() come before any output.
Incorrect code: Especially when using older PHP versions without http_response_code(), it is easy to set a status code inaccurately. It is important to know the exact syntax and meaning of each status code.

Creating Custom Status Codes

The HTTP protocol defines a set of standard status codes intended for specific situations. But what if you feel that none of these codes exactly conveys what you want to communicate? This raises the question of whether and how to create custom status codes in PHP.

How to do it:

Technically, using the header() function, you can send any three-digit status code along with a message:

header('HTTP/1.1 599 Custom Status Message‘);

In this example, the status code "599" is sent with the message "Custom Status Message".

Should you do it?

In general, creating custom status codes is not recommended for several reasons:

Standardization: The standardized HTTP status codes are designed to cover a wide range of scenarios. They are recognized globally and understood by many tools, proxies, bots, and, of course, browsers. A custom status code will likely not be recognized or misunderstood by the majority of these tools.
Confusion: Custom status codes can lead to confusion for other developers or systems interacting with your application.
Future collisions: A custom status code you define might be standardized in a future HTTP specification but with a different meaning. That can lead to unexpected problems.
Lack of support: Some systems may not handle non-standardized codes properly and simply interpret them as "500 Internal Server Error" or exhibit other unexpected behaviors.

If you still feel that the existing status codes do not precisely describe your situation, consider using custom headers or providing a detailed error message in the response body. This allows you to provide additional information without compromising the meaning and clarity of standardized status codes.

Although PHP provides flexibility to create custom status codes, in most cases, it is best to stick with established, standardized codes.

Summary

Proper handling of HTTP status codes in PHP is both an art and a science. While the technical aspects, such as using the correct syntax and functions, are relatively straightforward, correctly managing status codes in complex applications requires a deep understanding of both HTTP and the specific requirements of the application at hand. Developers who take the time to understand and master the nuances of status code management will be better positioned to create robust, user-friendly web applications.

PHP: header

header('HTTP/1.0 404 Not Found‘);

header('HTTP/1.0 301 Moved Permanently‘);
header('Location: /new-url.php‘);

PHP: http_response_code

http_response_code(404)
http_response_code(402)