3.5 PSR-15 Middleware in TYPO3

Multiple middlewares must be implemented in multiple extensions

Middlewares in TYPO3 follow the PSR-15 standard

The MiddlewareProvider in TYPO3 requires at least PHP version 7.3

Middlewares are the successor of CenterWares in PHP version 5.6

TYPO3 comes with some default middlewares that can be overwritten by custom implementations

By developing an extension with the class Classes/Domain/Backend/Middleware.php

By developing an extension with the class Classes/Domain/Middleware/Backend.php

By extending the core class \TYPO3\CMS\Core\AbstractMiddleware

By registering the custom middleware class in file Configuration/RequestMiddlewares.php

If the same middleware key is used multiple times, these middlewares are executed in random order

If the same middleware key is used multiple times, previous middlewares are overwritten (replaced)

Middlewares provided by the TYPO3 core can not be overwritten for security reasons

Custom middlewares can be positioned in the process stack by specifying a “before” rule

Custom middlewares can be positioned in the process stack by specifying a “after” rule

In the TYPO3 backend under SYSTEM → Configuration → HTTP Middlewares (PSR-15)

In the TYPO3 backend under ADMIN TOOLS → Environment → Environment Overview

By executing the CLI command typo3/sysext/core/bin/typo3 configuration:middlewares

By reviewing the file typo3conf/MiddlewaresConfiguration.php