UrlHelper

Zend\Expressive\Helper\UrlHelper provides the ability to generate a URI path based on a given route defined in the Zend\Expressive\Router\RouterInterface. If injected with a route result, and the route being used was also the one matched during routing, you can provide a subset of routing parameters, and any not provided will be pulled from those matched.

Usage

When you have an instance, use either its generate() method, or call the instance as an invokable:

// Using the generate() method:
$url = $helper->generate('resource', ['id' => 'sha1']);

// is equivalent to invocation:
$url = $helper('resource', ['id' => 'sha1']);

The signature for both is:

function (
    $routeName,
    array $routeParams = [],
    $queryParams = [],
    $fragmentIdentifier = null,
    array $options = []
) : string

Where:

  • $routeName is the name of a route defined in the composed router. You may omit this argument if you want to generate the path for the currently matched request.
  • $routeParams is an array of substitutions to use for the provided route, with the following behavior:
    • If a RouteResult is composed in the helper, and the $routeName matches it, the provided $params will be merged with any matched parameters, with those provided taking precedence.
    • If a RouteResult is not composed, or if the composed result does not match the provided $routeName, then only the $params provided will be used for substitutions.
    • If no $params are provided, and the $routeName matches the currently matched route, then any matched parameters found will be used. parameters found will be used.
    • If no $params are provided, and the $routeName does not match the currently matched route, or if no route result is present, then no substitutions will be made.
  • $queryParams is an array of query string arguments to include in the generated URI.
  • $fragmentIdentifier is a string to use as the URI fragment.
  • $options is an array of options to provide to the router for purposes of controlling URI generation. As an example, zend-router can consume "translator" and "text_domain" options in order to provide translated URIs.

Each method will raise an exception if:

  • No $routeName is provided, and no RouteResult is composed.
  • No $routeName is provided, a RouteResult is composed, but that result represents a matching failure.
  • The given $routeName is not defined in the router.

Signature changes

The signature listed above is current as of version 3.0.0 of zendframework/zend-expressive-helpers. Prior to that version, the helper only accepted the route name and route parameters.

Creating an instance

In order to use the helper, you will need to instantiate it with the current RouterInterface. The factory Zend\Expressive\Helper\UrlHelperFactory has been provided for this purpose, and can be used trivially with most dependency injection containers implementing PSR-11 Container. Additionally, it is most useful when injected with the current results of routing, which requires registering middleware with the application that can inject the route result. The following steps should be followed to register and configure the helper:

  • Register the UrlHelper as a service in your container, using the provided factory.
  • Register the UrlHelperMiddleware as a service in your container, using the provided factory.
  • Register the UrlHelperMiddleware as pipeline middleware, immediately following the routing middleware.

Registering the helper service

The following examples demonstrate programmatic registration of the UrlHelper service in your selected dependency injection container.

use Zend\Expressive\Helper\UrlHelper;
use Zend\Expressive\Helper\UrlHelperFactory;

// zend-servicemanager:
$services->setFactory(UrlHelper::class, UrlHelperFactory::class);

// Pimple:
$pimple[UrlHelper::class] = function ($container) {
    $factory = new UrlHelperFactory();
    return $factory($container);
};

// Aura.Di:
$container->set(UrlHelperFactory::class, $container->lazyNew(UrlHelperFactory::class));
$container->set(
    UrlHelper::class,
    $container->lazyGetCall(UrlHelperFactory::class, '__invoke', $container)
);

The following dependency configuration will work for all three when using the Expressive skeleton:

return ['dependencies' => [
    'factories' => [
        UrlHelper::class => UrlHelperFactory::class,
    ],
]]

UrlHelperFactory requires RouterInterface

The factory requires that a service named Zend\Expressive\Router\RouterInterface is present, and will raise an exception if the service is not found.

Registering the pipeline middleware

To register the UrlHelperMiddleware as pipeline middleware following the routing middleware:

use Zend\Expressive\Helper\UrlHelperMiddleware;

// Programmatically:
$app->pipeRoutingMiddleware();
$app->pipe(UrlHelperMiddleware::class);
$app->pipeDispatchMiddleware();

// Or use configuration:
// [
//     'middleware_pipeline' => [
//         /* ... */
//         Zend\Expressive\Application::ROUTING_MIDDLEWARE,
//         ['middleware' => UrlHelperMiddleware::class],
//         Zend\Expressive\Application::DISPATCH_MIDDLEWARE,
//         /* ... */
//     ],
// ]
//
// Alternately, create a nested middleware pipeline for the routing, UrlHelper,
// and dispatch middleware:
// [
//     'middleware_pipeline' => [
//         /* ... */
//         'routing' => [
//             'middleware' => [
//                 Zend\Expressive\Application::ROUTING_MIDDLEWARE,
//                 UrlHelperMiddleware::class
//                 Zend\Expressive\Application::DISPATCH_MIDDLEWARE,
//             ],
//             'priority' => 1,
//         ],
//         /* ... */
//     ],
// ]

The following dependency configuration will work for all three when using the Expressive skeleton:

return [
    'dependencies' => [
        'factories' => [
            UrlHelper::class => UrlHelperFactory::class,
            UrlHelperMiddleware::class => UrlHelperMiddlewareFactory::class,
        ],
    ],
    'middleware_pipeline' => [
        Zend\Expressive\Application::ROUTING_MIDDLEWARE,
        ['middleware' => UrlHelperMiddleware::class],
        Zend\Expressive\Application::DISPATCH_MIDDLEWARE,
    ],
];

// OR:
return [
    'dependencies' => [
        'factories' => [
            UrlHelper::class => UrlHelperFactory::class,
            UrlHelperMiddleware::class => UrlHelperMiddlewareFactory::class,
        ],
    ],
    'middleware_pipeline' => [
        'routing' => [
            'middleware' => [
                Zend\Expressive\Application::ROUTING_MIDDLEWARE,
                UrlHelperMiddleware::class,
                Zend\Expressive\Application::DISPATCH_MIDDLEWARE,
            ],
            'priority' => 1,
        ],
    ],
];

Skeleton configures helpers

If you started your project using the Expressive skeleton package, the UrlHelper and UrlHelperMiddleware factories are already registered for you, as is the UrlHelperMiddleware pipeline middleware.

Using the helper in middleware

Compose the helper in your middleware (or elsewhere), and then use it to generate URI paths:

use Zend\Expressive\Helper\UrlHelper;

class FooMiddleware
{
    private $helper;

    public function __construct(UrlHelper $helper)
    {
        $this->helper = $helper;
    }

    public function __invoke($request, $response, callable $next)
    {
        $response = $response->withHeader(
            'Link',
            $this->helper->generate('resource', ['id' => 'sha1'])
        );
        return $next($request, $response);
    }
}

Base Path support

If your application is running under a subdirectory, or if you are running pipeline middleware that is intercepting on a subpath, the paths generated by the router may not reflect the base path, and thus be invalid. To accommodate this, the UrlHelper supports injection of the base path; when present, it will be prepended to the path generated by the router.

As an example, perhaps you have middleware running to intercept a language prefix in the URL; this middleware could then inject the UrlHelper with the detected language, before stripping it off the request URI instance to pass on to the router:

use Interop\Http\ServerMiddleware\DelegateInterface;
use Interop\Http\ServerMiddleware\MiddlewareInterface;
use Locale;
use Psr\Http\Message\ServerRequestInterface;
use Zend\Expressive\Helper\UrlHelper;

class LocaleMiddleware implements MiddlewareInterface
{
    private $helper;

    public function __construct(UrlHelper $helper)
    {
        $this->helper = $helper;
    }

    public function process(ServerRequestInterface $request, DelegateInterface $delegate)
    {
        $uri = $request->getUri();
        $path = $uri->getPath();
        if (! preg_match('#^/(?P<locale>[a-z]{2,3}([-_][a-zA-Z]{2}|))/#', $path, $matches)) {
            return $delegate->process($request);
        }

        $locale = $matches['locale'];
        Locale::setDefault(Locale::canonicalize($locale));
        $this->helper->setBasePath($locale);

        return $delegate->process($request->withUri(
            $uri->withPath(substr($path, (strlen($locale) + 1)))
        ));
    }
}

(Note: if the base path injected is not prefixed with /, the helper will add the slash.)

Paths generated by the UriHelper from this point forward will have the detected language prefix.

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