Hooks

Installation

composer require glhd/hooks

Usage

The hooks package provides two types of hooks: hooking into class execution, and hooking into view rendering.

Within Classes

To make a class "hook-able" you need to use the Hookable trait. In your code, you can add callHook() calls anywhere that you want to allow outside code to execute. For example, if you were implementing a Session class, you might want to allow code to hook into before the session starts, and before the session saves:

use Glhd\Hooks\Hookable;

class MySessionClass implements SessionHandlerInterface
{
    use Hookable;
    
    public function public open(string $path, string $name): bool
    {
        $this->callHook('beforeOpened', $name);
        // ...
    }
    
    public function write(string $id, string $data): bool
    {
        $this->callHook('beforeWritten');
        // ..
    }
}

Now, you can hook into these points from elsewhere in your app:

// Get all the available hook points
$hooks = Session::hook();

// Register your custom code to execute at those points
$hooks->beforeOpened(function($name) {
    Log::info("Starting session '$name'");
});

$hooks->beforeWritten(function() {
    Log::info('Writing session to storage');
});

Now, whenever MySessionClass::open is called, a "Starting session '<session name>'" message will be logged, and whenever MySessionClass::write is called, a "Writing session to storage" message will be logged.

Hook Priority

You can pass an additional int priority to your hooks, to account for multiple hooks attached to the same point. For example:

$hooks->beforeOpened(fn($name) => Log::info('Registered First'), 500);
$hooks->beforeOpened(fn($name) => Log::info('Registered Second'), 100);

Would cause "Registered Second" to log before "Registered First". If you don't pass a priority, the default of 1000 will be used. All hooks at the same priority will be executed in the order they were registered.

Stopping Propagation

Hooks can halt further hooks from running with a special stopPropagation call (just like JavaScript). All hooks receive a Context object as the last argument. Calling stopPropagation on this object will halt any future hooks from running:

use Glhd\Hooks\Context;

$hooks->beforeOpened(function($name) {
    Log::info('Lower-priority hook');
}, 500);

$hooks->beforeOpened(function($name, Context $context) {
    Log::info('Higher-priority hook');
    $context->stopPropagation();
}, 100);

In the above case, the 'Lower-priority hook' message will never be logged, because a higher-priority hook stopped propagation before it could run.

Passing data between your code and hooks

There are three different ways that data gets passed in and out of hooks:

1. Passing arguments into hooks (one-way)
2. Returning values from hooks (one-way)
3. Passing data into hooks that can be mutated by hooks (two-way)

One-way data

Options 1 and 2 are relatively simple. Any positional argument that you pass to callHook will be forwarded to the hook as-is. In our example above, the beforeOpened call passed $name to its hooks, and our hook accepted $name as its first argument.

A collection of returned values from our hooks is available to the calling code. For example, if we wanted to allow hooks to add extra recipients to all email sent by our Mailer class, we might do something like:

use Glhd\Hooks\Hookable;

class Mailer
{
    use Hookable;
    
    protected function setRecipients() {
        $recipients = $this->callHook('preparingRecipients')
            ->filter()
            ->append($this->to);
            
        $this->service->setTo($recipients);
    }
}

// Always add QA to recipient list in staging
if (App::environment('staging')) {
    Mailer::hook()->preparingRecipients(fn() => 'qa@myapp.com');
}

It's important to note that you will always get a collection of results, though, even if there is only one hook attached to a call, because you never know how many hooks may be registered.

Two-way data

Sometimes you need your calling code and hooks to pass the same data in two directions. A common use-case for this is when you want your hooks to have the option to abort execution, or change some default behavior. You can do this by passing named arguments to the call, which will be added to the Context object that is passed as the last argument to your hook.

For example, what if we want hooks to have the ability to prevent mail from sending at all? We might do that with something like:

use Glhd\Hooks\Hookable;

class Mailer
{
    use Hookable;
    
    protected function send() {
        $result = $this->callHook('beforeSend', $this->message, shouldSend: true);
        
        if ($result->shouldSend) {
            $this->service->send();
        }
    }
}

// Never send mail to mailinator addresses
Mailer::hook()->beforeSend(function($message, $context) {
    if (str_contains($message->to, '@mailinator.com')) {
        $context->shouldSend = false;
    }
});

When to use class hooks

Class hooks are mostly useful for package code that needs to be extensible without knowing how it will exactly be extended. The Laravel framework provides similar extension points, like Queue::createPayloadUsing.

In general, you should avoid using class hooks in your application code unless you are dealing with particularly complex conditional logic that really warrants this approach.

Within Views

Sometimes you may want to make certain views "hook-able" as well. For example, suppose you have an ecommerce website that sends out email receipts, and you want to occasionally add promotions or other contextual content to the email message. Rather than constantly adding and removing a bunch of @if calls, you can use a hook:

{{-- emails/receipt.blade.php --}}
Thank you for shopping at…

<x-hook name="intro" />

Your receipt info…

<x-hook name="footer" />

Now you have two spots that you can hook into…

// Somewhere in a `PromotionsServiceProvider` class, perhaps…

if ($this->isInCyberMondayPromotionalPeriod()) {
    View::hook('emails.receipt', 'intro', fn() => view('emails.promotions._cyber_monday_intro'));
}

if (Auth::user()->isNewRegistrant()) {
    View::hook('emails.receipt', 'footer', fn() => view('emails.promotions._thank_you_for_first_purchase'));
}

The View::hook method accepts 4 arguments. The first is the view name that you're hooking into; the second is the name of the hook itself. The third argument can either be a view (or anything that implements the Htmlable contract), or a closure that returns anything that Blade can render. Finally, the fourth argument is a priority value—the lower the priority, the earlier it will be rendered (if there are multiple things hooking into the same spot). If you do not provide a priority, it will be set the 1000 by default.

Explicitly Setting View Name

The <x-hook> Blade component can usually infer what view it's being rendered inside. Depending on how your views are rendered, though, you may need to explicitly pass the view name to the component. You can do that by passing an additional view prop:

<x-hook view="emails.receipt" name="intro" />

This is a requirement that we hope to improve in a future release!

View Hook Attributes

It's possible to pass component attributes to your hooks, using regular Blade syntax:

<x-hook name="status" status="Demoing hooks" />

Your hooks will then receive the status value (and any other attributes you pass):

View::hook('my.view', 'status', function($attributes) {
    assert($attributes['status'] === 'Demoing hooks');
});

If you pass the hook a Laravel view, any attributes will automatically be forwarded. This means that you can use the $status variable inside your view. For example, given the following views:

{{-- my/view.blade.php --}}
<x-hook name="status" status="Demoing hooks" />

{{-- my/hook.blade.php --}}
<div class="alert">
    Your current status is '{{ $status }}'
</div>

The following hook code would automatically forward the value "Demoing hooks" as the $status attribute in your my.hook view:

View::hook('my.view', 'status', view('my.hook'));