What is the implementation principle of php middleware

PHP middleware implementation principle: Middleware forms a chain, and when the request reaches the application, they process the request in order. Each middleware can inspect, modify a request, or return a response. The middleware class implements the MiddlewareInterface interface and defines the process() and setNext() methods. The process() method processes the request, and the setNext() method sets the next middleware. The chain is started by calling the process() method of the first middleware. The application is the last code in the chain to be executed.

The implementation principle of PHP middleware

PHP middleware is a popular mechanism for processing Insert logic into your application before or after a client request. It works as follows:

1. Request life cycle

• When a request reaches a PHP application, it passes through a series of middleware.
• Each middleware can inspect the request, modify it or return a response.
• If a middleware returns a response, the life cycle of the request ends and execution will not continue.

2. Middleware class

• The middleware class implements the MiddlewareInterface interface.
• This interface defines two methods: process() and setNext().

3. process() method

• process() method processes the request.
• It receives a ServerRequestInterface object and a RequestHandlerInterface object.
• ServerRequestInterface The object contains information about the request.
• RequestHandlerInterface The object is the next middleware or application callback function. The
• process() method can modify the request, return a response, or call $handler->handle() to continue processing.

4. setNext() method

• setNext() method sets the next middleware to be executed.
• If the next middleware is not set, the request will continue to the application.

5. Middleware chain

• Middleware forms a chain where each middleware calls the next.
• The application starts the chain by calling the process() method of the first middleware.

6. Application

• The application is the code that is executed after being called by all middleware.
• It is usually responsible for processing requests and returning responses.

Example

The following example shows a simple PHP middleware that adds a header to the request:

class AddHeaderMiddleware implements MiddlewareInterface
{
    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler)
    {
        $request = $request->withAddedHeader('X-Custom-Header', 'My Value');
        return $handler->handle($request);
    }
}

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