Quick Start: Using the Skeleton + Installer

The easiest way to get started with Expressive is to use the skeleton application and installer. The skeleton provides a generic structure for creating your applications, and prompts you to choose a router, dependency injection container, template renderer, and error handler from the outset.

Create a new project

First, we'll create a new project, using Composer's create-project command:

$ composer create-project zendframework/zend-expressive-skeleton expressive

This will prompt you to choose:

Start a web server

The Skeleton + Installer creates a full application structure that's ready-to-go when complete. You can test it out using built-in web server.

From the project root directory, execute the following:

$ composer run --timeout=0 serve

This starts up a web server on localhost port 8080; browse to http://localhost:8080/ to see if your application responds correctly!

Setting a timeout

Composer commands time out after 300 seconds (5 minutes). On Linux-based systems, the php -S command that composer serve spawns continues running as a background process, but on other systems halts when the timeout occurs.

As such, we recommend running the serve script using a timeout. This can be done by using composer run to execute the serve script, with a --timeout option. When set to 0, as in the previous example, no timeout will be used, and it will run until you cancel the process (usually via Ctrl-C). Alternately, you can specify a finite timeout; as an example, the following will extend the timeout to a full day:

$ composer run --timeout=86400 serve

Development Tools

Starting in version 2 of the skeleton, we ship tools to make development easier.

Development Mode

zf-development-mode allows you to enable and disable development mode from your cli.

$ composer development-enable  # enable development mode
$ composer development-disable # disable development mode
$ composer development-status  # show development status

The development configuration is set in config/autoload/development.local.php.dist. It also allows you to specify configuration and modules that should only be enabled when in development, and not when in production.

Clear config cache

Production settings are the default, which means enabling the configuration cache. However, it must be easy for developers to clear the configuration cache. That's what this command does.

$ composer clear-config-cache

Testing Your Code

PHPUnit and PHP_CodeSniffer are now installed by default. To execute tests and detect coding standards violations, run the following command:

$ composer check

Security Advisories

We have included the security-advisories package to notify you about installed dependencies with known security vulnerabilities. Each time you run composer update, composer install, or composer require, it prevents installation of software with known and documented security issues.

Modules

Composer will prompt you during installation to ask if you want a minimal application (no structure or default middleware provided), flat application (all source code under the same tree, and the default selection), or modular application. This latter option is new in the version 2 series, and allows you to segregate discrete areas of application functionality into modules, which can contain source code, templates, assets, and more; these can later be repackaged for re-use if desired.

Support for modules is available via the zend-component-installer and zend-config-aggregator packages; the zend-expressive-tooling. package provides tools for creating and manipulating modules in your application.

Component Installer

Whenever you add a component or module that exposes itself as such, the zend-component-installer composer plugin will prompt you, asking if and where you want to inject its configuration. This ensures that components are wired automatically for you.

In most cases, you will choose to inject in the config/config.php file; for tools intended only for usage during development, choose config/development.config.php.dist.

Config Aggregator

The zend-config-aggregator library collects and merges configuration from different sources. It also supports configuration caching.

As an example, your config/config.php file might read as follows in order to aggregate configuration from development mode settings, application configuration, and theoretical User, Blog, and App modules:

<?php // config/config.php

$aggregator = new ConfigAggregator([
    // Module configuration
    App\ConfigProvider::class,
    BlogModule\ConfigProvider::class,
    UserModule\ConfigProvider::class,

    // Load application config in a pre-defined order in such a way that local settings
    // overwrite global settings. (Loaded as first to last):
    //   - `global.php`
    //   - `*.global.php`
    //   - `local.php`
    //   - `*.local.php`
    new PhpFileProvider('config/autoload/{{,*.}global,{,*.}local}.php'),

    // Load development config if it exists
    new PhpFileProvider('config/development.config.php'),
], 'data/config-cache.php');

return $aggregator->getMergedConfig();

The configuration is merged in the same order as it is passed, with later entries having precedence.

Config Providers

ConfigAggregator works by aggregating "Config Providers" passed to its constructor. Each provider should be a callable class that requires no constructor parameters, where invocation returns a configuration array (or a PHP generator) to be merged.

Libraries or modules can have configuration providers that provide default values for a library or module. For the UserModule\ConfigProvider class loaded in the ConfigAggregator above, the ConfigProvider might look like this:

<?php

namespace UserModule;

class ConfigProvider
{
    /**
     * Returns the configuration array
     *
     * To add some sort of a structure, each section is defined in a separate
     * method which returns an array with its configuration.
     *
     * @return array
     */
    public function __invoke()
    {
        return [
            'dependencies' => $this->getDependencies(),
            'users'        => $this->getConfig(),
        ];
    }

    /**
     * Returns the container dependencies
     *
     * @return array
     */
    public function getDependencies()
    {
        return [
            'factories'  => [
                Action\LoginAction::class =>
                    Factory\Action\LoginActionFactory::class,

                Middleware\AuthenticationMiddleware::class =>
                    Factory\Middleware\AuthenticationMiddlewareFactory::class,
            ],
        ];
    }

    /**
     * Returns the default module configuration
     *
     * @return array
     */
    public function getConfig()
    {
        return [
            'paths' => [
                'enable_registration' => true,
                'enable_username'     => false,
                'enable_display_name' => true,
            ],
        ];
    }
}

expressive-module command

To aid in the creation, registration, and deregistration of modules in your application, the installer will add the zendframework/zend-expressive-tooling as a development requirement when you choose the modular application layout.

The tool is available from your application root directory via ./vendor/bin/expressive-module. For brevity, we will only reference the tool's name, expressive-module, when describing its capabilities.

This tool provides the following functionality:

You can find out more about its features in the command line tooling documentation.

Adding Middleware

The skeleton makes the assumption that you will be writing your middleware as classes, and uses piping and routing to add your middleware.

Piping

Piping is a foundation feature of the underlying zend-stratigility implementation. You can setup the middleware pipeline in config/pipeline.php. In this section, we'll demonstrate setting up a basic pipeline that includes error handling, segregated applications, routing, middleware dispatch, and more.

The error handler should be the first (most outer) middleware to catch all exceptions.

$app->pipe(ErrorHandler::class);
$app->pipe(ServerUrlMiddleware::class);  

After the ErrorHandler you can pipe more middleware that you want to execute on every request, such as bootstrapping, pre-conditions, and modifications to outgoing responses:

$app->pipe(ServerUrlMiddleware::class);  

Piped middleware may be either callables or service names. Middleware may also be passed as an array; each item in the array must resolve to middleware eventually (i.e., callable or service name); underneath, Expressive creates Zend\Stratigility\MiddlewarePipe instances with each of the middleware listed piped to it.

Middleware can be attached to specific paths, allowing you to mix and match applications under a common domain. The handlers in each middleware attached this way will see a URI with the MATCHED PATH SEGMENT REMOVED!!!

$app->pipe('/api', $apiMiddleware);
$app->pipe('/docs', $apiDocMiddleware);
$app->pipe('/files', $filesMiddleware);    

Next, you should register the routing middleware in the middleware pipeline:

$app->pipeRoutingMiddleware();

Add more middleware that needs to introspect the routing results; this might include:

$app->pipe(ImplicitHeadMiddleware::class);
$app->pipe(ImplicitOptionsMiddleware::class);
$app->pipe(UrlHelperMiddleware::class);

Next, register the dispatch middleware in the middleware pipeline:

$app->pipeDispatchMiddleware();

At this point, if no response is return by any middleware, we need to provide a way of notifying the user of this; by default, we use the NotFoundHandler, but you can provide any other fallback middleware you wish:

$app->pipe(NotFoundHandler::class);

The full example then looks something like this:

// In config/pipeline.php:

use Zend\Expressive\Helper\ServerUrlMiddleware;
use Zend\Expressive\Helper\UrlHelperMiddleware;
use Zend\Expressive\Middleware\ImplicitHeadMiddleware;
use Zend\Expressive\Middleware\ImplicitOptionsMiddleware;
use Zend\Expressive\Middleware\NotFoundHandler;
use Zend\Stratigility\Middleware\ErrorHandler;

$app->pipe(ErrorHandler::class);
$app->pipe(ServerUrlMiddleware::class);

// These assume that the variables listed are defined in this scope:
$app->pipe('/api', $apiMiddleware);
$app->pipe('/docs', $apiDocMiddleware);
$app->pipe('/files', $filesMiddleware);

$app->pipeRoutingMiddleware();
$app->pipe(ImplicitHeadMiddleware::class);
$app->pipe(ImplicitOptionsMiddleware::class);
$app->pipe(UrlHelperMiddleware::class);
$app->pipeDispatchMiddleware();

$app->pipe(NotFoundHandler::class);

Routing

Routing is an additional feature provided by Expressive. Routing is setup in config/routes.php.

You can setup routes with a single request method:

$app->get('/', App\Action\HomePageAction::class, 'home');
$app->post('/album', App\Action\AlbumCreateAction::class, 'album.create');
$app->put('/album/:id', App\Action\AlbumUpdateAction::class, 'album.put');
$app->patch('/album/:id', App\Action\AlbumUpdateAction::class, 'album.patch');
$app->delete('/album/:id', App\Action\AlbumDeleteAction::class, 'album.delete');

Or with multiple request methods:

$app->route('/contact', App\Action\ContactAction::class, ['GET', 'POST', ...], 'contact');

Or handling all request methods:

$app->route('/contact', App\Action\ContactAction::class)->setName('contact');

Alternately, to be explicit, the above could be written as:

$app->route(
  '/contact',
  App\Action\ContactAction::class,
  Zend\Expressive\Router\Route::HTTP_METHOD_ANY,
  'contact'
);  

We recommend a single middleware class per combination of route and request method.

Next Steps

The skeleton provides a default structure for templates, if you choose to use them. Let's see how you can create your first vanilla middleware, and templated middleware.

Creating middleware

To create middleware, create a class implementing Interop\Http\ServerMiddleware\MiddlewareInterface. This interface defines a single method, process(), which accepts a Psr\Http\Message\ServerRequestInterface instance and an Interop\Http\ServerMiddleware\DelegateInterface instance.

Legacy double-pass middleware

Prior to Expressive 2.0, the default middleware style was what is termed "double-pass", for the fact that it passes both the request and response between layers. This middleware did not require an interface, and relied on a conventional definition of:

use Psr\Http\Message;

function (
  Message\ServerRequestInterface $request,
  Message\ResponseInterface $response,
  callable $next
) : Message\ResponseInterface

While this style of middleware is still quite wide-spread and used in a number of projects, it has some flaws. Chief among them is the fact that middleware should not rely on the $response instance provided to them (as it may have modifications unacceptable for the current context), and that a response returned from inner layers may not be based off the $response provided to them (as inner layers may create and return a completely different response).

Starting in Expressive 2.0, we add support for http-interop/http-middleware, which is a working group of PHP-FIG dedicated to creating a common middleware standard. This middleware uses what is termed a "single-pass" or "lambda" architecture, whereby only the request instance is passed between layers. We now recommend writing middleware using the http-middleware interfaces for all new middleware.

Middleware using the double-pass style is still accepted by Expressive, but support for it will be discontinued once http-middleware is formally approved by PHP-FIG.

The skeleton defines an App namespace for you, and suggests placing middleware under the namespace App\Action.

Let's create a "Hello" action. Place the following in src/App/Action/HelloAction.php:

<?php
namespace App\Action;

use Interop\Http\ServerMiddleware\DelegateInterface;
use Interop\Http\ServerMiddleware\MiddlewareInterface;
use Psr\Http\Message\ServerRequestInterface;
use Zend\Diactoros\Response\HtmlResponse;

class HelloAction implements MiddlewareInterface
{
    public function process(ServerRequestInterface $request, DelegateInterface $delegate)
    {
        // On all PHP versions:
        $query  = $request->getQueryParams();
        $target = isset($query['target']) ? $query['target'] : 'World';

        // Or, on PHP 7+:
        $target = $request->getQueryParams()['target'] ?? 'World';

        $target = htmlspecialchars($target, ENT_HTML5, 'UTF-8');

        return new HtmlResponse(sprintf(
            '<h1>Hello, %s!</h1>',
            $target
        ));
    }
}

The above looks for a query string parameter "target", and uses its value to provide a message, which is then returned in an HTML response.

Now we need to inform the application of this middleware, and indicate what path will invoke it. Open the file config/autoload/dependencies.global.php. Edit that file to add an invokable entry for the new middleware:

return [
    'dependencies' => [
        /* ... */
        'invokables' => [
            App\Action\HelloAction::class => App\Action\HelloAction::class,
            /* ... */
        ],
        /* ... */
    ],
];

Now open the file config/routes.php, and add the following at the bottom of the file:

$app->get('/hello', App\Action\HelloAction::class, 'hello');

Once you've completed the above, give it a try by going to each of the following URIs:

You should see the message change as you go between the two URIs!

Using templates

You likely don't want to hardcode HTML into your middleware; so, let's use templates. This particular exercise assumes you chose to use the Plates integration.

Templates are installed under the templates/ subdirectory. By default, we also register the template namespace app to correspond with the templates/app subdirectory. Create the file templates/app/hello-world.phtml with the following contents:

<?php $this->layout('layout::default', ['title' => 'Greetings']) ?>

<h2>Hello, <?= $this->e($target) ?></h2>

Now that we have a template, we need to:

Replace your src/App/Action/HelloAction.php file with the following contents:

<?php
namespace App\Action;

use Interop\Http\ServerMiddleware\DelegateInterface;
use Interop\Http\ServerMiddleware\MiddlewareInterface;
use Psr\Http\Message\ServerRequestInterface;
use Zend\Diactoros\Response\HtmlResponse;
use Zend\Expressive\Template\TemplateRendererInterface;

class HelloAction implements MiddlewareInterface
{
    private $renderer;

    public function __construct(TemplateRendererInterface $renderer)
    {
        $this->renderer = $renderer;
    }

    public function process(ServerRequestInterface $request, DelegateInterface $delegate)
    {
        // On all PHP versions:
        $query  = $request->getQueryParams();
        $target = isset($query['target']) ? $query['target'] : 'World';

        // Or, on PHP 7+:
        $target = $request->getQueryParams()['target'] ?? 'World';

        return new HtmlResponse(
            $this->renderer->render('app::hello-world', ['target' => $target])
        );
    }
}

The above modifies the class to accept a renderer to the constructor, and then calls on it to render a template. Note that we no longer need to escape our target; the template takes care of that for us.

How does the template renderer get into the action? The answer is dependency injection.

For the next part of the example, we'll be creating and wiring a factory for creating the HelloAction instance; the example assumes you used the default selection for a dependency injection container, zend-servicemanager.

zend-servicemanager provides a tool for generating factories based on reflecting a class; we'll use that to generate our factory:

$ ./vendor/bin/generate-factory-for-class "App\\Action\\HelloAction" > src/App/Action/HelloActionFactory.php

With that in place, we'll now update our configuration. Open the file config/autoload/dependencies.global.php; we'll remove the invokables entry we created previously, and add a factories entry:

return [
    'dependencies' => [
        /* ... */
        'invokables' => [
            // Remove this entry:
            App\Action\HelloAction::class => App\Action\HelloAction::class,
        ],
        'factories' => [
            /* ... */
            // Add this:
            App\Action\HelloAction::class => App\Action\HelloActionFactory::class,
        ],
        /* ... */
    ],
];

Save that file, and now re-visit the URIs:

Your page should now have the same layout as the landing page of the skeleton application!

Congratulations!

Congratulations! You've now created your application, and started writing middleware! It's time to start learning about the rest of the features of Expressive: