Migration to Mezzio 3.0

Mezzio 3.0 should not result in many upgrade problems for users. However, starting in this version, we offer a few changes affecting the following that you should be aware of, and potentially update your application to adopt:

PHP 7.1 support

Starting in Mezzio 3.0 we support only PHP 7.1+.

PSR-15 Support

All middleware and delegators now implement interfaces from PSR-15 instead of http-interop/http-middleware (a PSR-15 precursor). This means the following changes were made throughout Mezzio:

  • The process() method of all middleware now type hint the second argument against the PSR-15 RequestHandlerInterface, instead of the previous DelegateInterface.

  • The process() method of all middleware now have a return type hint of \Psr\Http\Message\ResponseInterface.

  • All "delegators" have become request handlers: these now implement the PSR-15 interface RequestHandlerInterface instead of the former DelegateInterface.

  • The process() method of handlers (formerly delegators) have been renamed to handle() and given a return type hint of \Psr\Http\Message\ResponseInterface.

This change also affects all middleware you, as an application developer, have written, and your middleware will need to be update. We provide a tool for this via mezzio-tooling. Make sure that package is up-to-date (a version 1 release should be installed), and run the following:

$ ./vendor/bin/mezzio migrate:interop-middleware

This tool will locate any http-interop middleware and update it to PSR-15 middleware.

New dependencies

Mezzio adds the following packages as dependencies:

  • psr/http-server-middleware provides the PSR-15 interfaces, and replaces the previous dependency on http-interop/http-middleware.

  • mezzio/mezzio-router; previously, we depended on this package indirectly; now it is a direct requirement.

  • mezzio/mezzio-tooling; this was suggested previously, but is now required as a development dependency.

  • laminas/laminas-httphandlerrunner; this is now used for the purposes of marshaling the server request, dispatching the application, and emitting the response. The functionality is generalized enough to warrant a separate package.

New features

The following classes were added in version 3:

  • Mezzio\Container\ApplicationConfigInjectionDelegator is a delegator factory capable of piping and routing middleware from configuration. See the recipe on autowiring routes and pipeline middleware for more information.

  • Mezzio\Container\ApplicationPipelineFactory will produce an empty MiddlewarePipe for use with Mezzio\Application.

  • Mezzio\Container\EmitterFactory will produce a Laminas\HttpHandlerRunner\Emitter\EmitterStack instance for use with the RequestHandlerRunner instance composed by the Application. See the chapter on emitters for more details.

  • Mezzio\Container\MiddlewareContainerFactory will produce a MiddlewareContainer composing the application container instance.

  • Mezzio\Container\MiddlewareFactoryFactory will produce a MiddlewareFactory composing a MiddlewareContainer instance.

  • Mezzio\Container\RequestHandlerRunnerFactory will produce a Laminas\HttpHandlerRunner\RequestHandlerRunner instance for use with the Application instance. See the laminas-httphandlerrunner documentation for more details on this collaborator.

  • Mezzio\Container\ServerRequestErrorResponseGeneratorFactory will produce a Mezzio\Response\ServerRequestErrorResponseGenerator instance for use with the RequestHandlerRunner.

  • Mezzio\Container\ServerRequestFactoryFactory will produce a PHP callable capable of generating a PSR-7 ServerRequestInterface instance for use with the RequestHandlerRunner.

  • Mezzio\MiddlewareContainer decorates a PSR-11 container, and ensures that the values pulled are PSR-15 MiddlewareInterface instances. If the container returns a PSR-15 RequestHandlerInterface, it decorates it via Laminas\Stratigility\Middleware\RequestHandlerMiddleware. All other types result in an exception being thrown.

  • Mezzio\MiddlewareFactory allows creation of MiddlewareInterface instances from a variety of argument types, and is used by Application to allow piping and routing to middleware services, arrays of services, and more. It composes a MiddlewareContainer internally.

  • Mezzio\Response\ServerRequestErrorResponseGenerator can act as a response generator for the RequestHandlerRunner when its composed server request factory raises an exception.

Signature and behavior changes

The following signature changes were made that could affect class extensions and/or consumers.


Mezzio\Application was refactored dramatically for version 3.

If you were instantiating it directly previously, the constructor arguments are now, in order:

  • Mezzio\MiddlewareFactory
  • Laminas\Stratigility\MiddlewarePipeInterface
  • Mezzio\Router\RouteCollector
  • Laminas\HttpHandlerRunner\RequestHandlerRunner
  • Mezzio\Application::__construct(...)

Application no longer supports piping or routing to double-pass middleware. If you continue to need double-pass middleware (e.g., defined by a third-party library), use Laminas\Stratigility\doublePassMiddleware() to decorate it prior to piping or routing to it:

use Laminas\Diactoros\Response;

use function Laminas\Stratigility\doublePassMiddleware;

$app->pipe(doublePassMiddleware($someDoublePassMiddleware, new Response()));

$app->get('/foo', doublePassMiddleware($someDoublePassMiddleware, new Response()));

Additionally, the following methods were removed:

  • pipeRoutingMiddleware(): use pipe(\Mezzio\Router\Middleware\RouteMiddleware::class) instead.
  • pipeDispatchMiddleware(): use pipe(\Mezzio\Router\Middleware\DispatchMiddleware::class) instead.
  • getContainer()
  • getDefaultDelegate(): ensure you pipe middleware or a request handler capable of returning a response at the innermost layer; Mezzio\Handler\NotFoundHandler can be used for this.
  • getEmitter(): use the Laminas\HttpHandlerRunner\Emitter\EmitterInterface service from the container.
  • injectPipelineFromConfig(): use the new ApplicationConfigInjectionDelegator and/or the static method of the same name it defines.
  • injectRoutesFromConfig(): use the new ApplicationConfigInjectionDelegator and/or the static method of the same name it defines.


Mezzio\Container\ApplicationFactory no longer looks at the mezzio.programmatic_pipeline flag, nor does it inject pipeline middleware and/or routed middleware from configuration any longer.

If you want to use configuration-driven pipelines and/or middleware, you may register the new class Mezzio\Container\ApplicationConfigInjectionDelegator as a delegator factory on the Mezzio\Application service.


Mezzio\Container\NotFoundHandlerFactory now returns an instance of Mezzio\Handler\NotFoundHandler, instead of Mezzio\Middleware\NotFoundHandler (which has been removed).


Mezzio\Middleware\LazyLoadingMiddleware now composes a Mezzio\MiddlewareContainer instance instead of a more general PSR-11 container; this is to ensure that the value returned is a PSR-15 MiddlewareInterface instance.

Removed classes and traits

  • Mezzio\AppFactory was removed. If you were using it previously, either use Mezzio\Application directly, or a Laminas\Stratigility\MiddlewarePipe instance.

  • Mezzio\ApplicationConfigInjectionTrait; the functionality of this trait was replaced by the Mezzio\Container\ApplicationConfigInjectionDelegator.

  • Mezzio\Delegate\NotFoundDelegate; use Mezzio\Handler\NotFoundHandler instead. Its factory, Mezzio\Container\NotFoundDelegateFactory, was also removed.

  • Mezzio\Emitter\EmitterStack; use Laminas\HttpHandlerRunner\Emitter\EmitterStack instead.

  • Mezzio\IsCallableInteropMiddlewareTrait; there is no functional equivalent, nor a need for this functionality as of version 3.

  • Mezzio\MarshalMiddlewareTrait; the functionality of this trait was replaced by a combination of Mezzio\MiddlewareContainer and Mezzio\MiddlewareFactory.

  • Mezzio\Middleware\DispatchMiddleware; use Mezzio\Router\Middleware\DispatchMiddleware instead.

  • Mezzio\Middleware\ImplicitHeadMiddleware; use Mezzio\Router\Middleware\ImplicitHeadMiddleware instead.

  • Mezzio\Middleware\ImplicitOptionsMiddleware; use Mezzio\Router\Middleware\ImplicitOptionsMiddleware instead.

  • Mezzio\Middleware\NotFoundHandler; use Mezzio\Handler\NotFoundHandler instead.

  • Mezzio\Middleware\RouteMiddleware; use Mezzio\Router\Middleware\RouteMiddleware instead.


We provide a package you can add to your existing v2 application in order to upgrade it to version 3.

Before installing and running the migration tooling, make sure you have checked in your latest changes (assuming you are using version control), or have a backup of your existing code.

Install the migration tooling using the following command:

$ composer require --dev mezzio/mezzio-migration

Once installed, run the following command to migrate your application:

$ ./vendor/bin/mezzio-migration migrate

This package does the following:

  • Uninstalls all current dependencies (by removing the vendor/ directory).
  • Updates existing dependency constraints for known Mezzio packages to their latest stable versions. (See the tools README for details on what versions of which packages the tool uses.)
  • Adds development dependencies on laminas/laminas-component-installer and mezzio/mezzio-tooling.
  • Updates the config/pipeline.php file to:
    • add strict type declarations.
    • modify it to return a callable, per the v3 skeleton.
    • update the middleware pipeline as follows:
      • pipeRoutingMiddleware() becomes a pipe() operation referencing the mezzio-router RouteMiddleware.
      • pipeDispatchMiddleware() becomes a pipe() operation referencing the mezzio-router DispatchMiddleware.
      • update references to ImplicitHeadMiddleware to reference the version in mezzio-router.
      • update references to ImplicitOptionsMiddleware to reference the version in mezzio-router.
      • update references to Mezzio\Middleware\NotFoundHandler to reference Mezzio\Handler\NotFoundHandler.
      • add a pipe() entry for the mezzio-router MethodNotAllowedMiddleware.
  • Updates the config/routes.php file to:
    • add strict type declarations.
    • modify it to return a callable, per the v3 skeleton.
  • Replaces the public/index.php file with the latest version from the skeleton.
  • Updates config/container.php when Pimple or Aura.Di are in use:
    • For Pimple:
      • The package xtreamwayz/pimple-container-interop is replaced with laminas/laminas-pimple-config.
      • The Pimple variant of container.php from the v3 skeleton is used.
    • For Aura.Di
      • The package aura/di is replaced with laminas/laminas-auradi-config.
      • The Aura.Di variant of container.php from the v3 skeleton is used.
  • Executes ./vendor/bin/mezzio migrate:interop-middleware.
  • Executes ./vendor/bin/mezzio migrate:middleware-to-request-handler.
  • Runs ./vendor/bin/phpcbf if it is installed.

These steps should take care of most migration tasks.

It does not update unit tests. These cannot be automatically updated, due to the amount of variance in testing strategies.

When done, use a diffing tool to compare and verify all changes. Please be aware that the tool is not designed for edge cases; there may be things it does not do or cannot catch within your code. When unsure, refer to the other sections in this document to determine what else you may need to change.

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