HTTP caching library in PHP8.0: PSR-7

As web applications run longer and longer, server performance and data transfer speeds become bigger and bigger issues. HTTP caching is a way to deal with this problem. Caching commonly used resources on the client side can allow applications to respond to requests faster and reduce the load on the server. As a web development language, PHP 8.0 also has its own solution for handling HTTP caching, namely PSR-7.

PSR-7 is a PHP standard designed for HTTP messages, providing a unified interface for creating and processing HTTP request and response messages. It defines the basic components of an HTTP message (e.g. HTTP headers, request URI, HTTP method, HTTP body) and how to build, serialize and parse from them.

In the case of HTTP caching, an important role of PSR-7 is that it standardizes the HTTP message header, which is the standard for controlling caching. User agents can control caching behavior using header information such as Cache-Control, so using PSR-7 is crucial if we want to achieve efficient HTTP caching.

The following are some HTTP caching solutions that PSR-7 can provide:

1.ETag cache

ETag cache is an entity tag cache. When a client requests a resource, an ETag is added to the response header, which is stored by the client and sent back to the server the next time the same resource is requested. The server checks whether the client's ETag is the same as the server-side resource. If so, the server will return a response header with a 304 Not Modified response code and extract the resources from the client's cache, thus avoiding repeated transmission of resources and reducing the load on the server.

ETag caching can be easily implemented using PSR-7. By adding an ETag header to the response message, the ETag can be easily sent back to the client for the next request. The server uses the ETag value for comparison. If the values ​​are the same, it no longer sends the resource, but instead sends a 304 Not Modified response. Here is an example:

$response = new Response();
$response = $response

->withHeader('ETag', 'MyETagValue');

2. Last-Modified Cache

Last-Modified cache is an entity tag cache. The server adds a Last-Modified header to the response message header, whose value is the last modification time of the requested resource. When the client requests the same resource next time, it sends the Last-Modified header information in date and time format back to the server. The server will check whether this header information is the last modification time of the resource. If so, the server returns a response header with a 304 Not Modified response code and fetches the resource from the client's cache to reduce the load on the server.

Using psr-7, you can also easily implement Last-Modified caching. Code example:

$response = new Response();
$response = $response

->withHeader('Last-Modified', 'LastModifiedDate');

3. Cache-Control Cache Strategy

Cache -Control caching strategy is a method set in the response header to control the caching method. It reduces the client's requests, thereby reducing the load on the server. The Cache-Control header information has the following types:

• max-age: The maximum time for caching.
• no-cache: Can be cached, but each use requires valid verification.
• no-store: should not be cached.
• private/public: Cache is only for private clients/shareable.
• must-revalidate: Re-validation is required after expiration.
• stale-while-revalidate: After the cache time expires, old data will be returned while obtaining new data.
• stale-if-error: In case of network abnormality, if there is a cache, the cache will also be returned.

The following is an example of implementing the Cache-Control cache strategy through PSR-7. Just add the necessary information in the response header:

$response = new Response();
$response = $response

->withHeader('Cache-Control', 'max-age=3600');

Summary

PSR- 7 provides a standardized solution for creating and processing HTTP request and response messages, which is essential for achieving efficient HTTP caching. Using PSR-7, you can easily implement ETag caching, Last-Modified caching, and Cache-Control caching strategies. If you are building a web application using PHP 8.0 and need to implement efficient HTTP caching, give PSR-7 a try.

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