New Aura v2 Stable Releases, and More

New v2 releases, and hey, what’s this about Aura.Di finally getting auto-resolution of typehinted parameters?

First, we have brand new 2.0.0 stable releases of these v2 packages!

Next, the Aura.Di package just got bumped to 2.0.0-beta2. This package in particular has seen some great new improvements, most notably auto-resolution of typehinted constructor parameters, and a brand-new README. Check it out at https://github.com/auraphp/Aura.Di.

Emphasis not in original; read the whole notice at http://auraphp.com/blog/2014/09/03/new-releases/.

Auto-resolution of typehinted parameters is something I’ve been against since the beginning of Aura.Di. After having used implicit magical convention for a long time, I have learned to prefer explicit configuration. However, auto-resolution turned out to be relatively simple to add, and the tradeoff of not having to explicitly specify every lazyNew('ClassName') every time on every parameter seems reasonable. (One hopes one does not get burned later for having made this concession.)

On Project Structure; or, The Framework/App Is Not Special

(I apologize for the hasty writing here; this subject makes me impatient.)

Reading this post from Code Rabbi makes me reflect on project structure and organization. Frankly, most project structures (as from CodeIgniter, Cake, and all the popular frameworks since then) strike me as misdirected. They’re examples of why the project maintainers think their code is somehow special and different, and that the application built from it is also somehow special and different.

Your framework and application code are not special. Their code does not go in a special place. There’s no need for a top-level “app” directory with its own special subdirectories. There’s no need for a special naming convention to keep your different application-specfic code in specific places.

We had PSR-0, and now have PSR-4, and the Composer autoloader, to handle all that for you. Just use namespaces. All you need for code at the top level of your project is a “src” directory, where all your app code goes, just like all your library code goes in a “src” directory in a library package.

Instead of /app/controllers and /app/models, you have /src/Controller and /src/Model, or however else you want to organize your namespaced code. Then there’s no need for a special autoloading system or for hard-coded paths just for your application-level code. Add one single line to Composer that points to the src directory and voila, everything inside it loads for you.

That’s it. Nothing special. Just like every other library in your system.

(Again, this was hastily written. Please ask for clarficiation if you feel you need it.)

DRY is about Knowledge

From Matthias Verraes:

“Don’t Repeat Yourself” was never about code. It’s about knowledge. It’s about cohesion. If two pieces of code represent the exact same knowledge, they will always change together. Having to change them both is risky: you might forget one of them. On the other hand, if two identical pieces of code represent different knowledge, they will change independently. De-duplicating them introduces risk, because changing the knowledge for one object, might accidentally change it for the other object.

This is a great observation, one I had not considered before. It makes me feel a lot better about the very few and very minor duplications of code in the various independent and decoupled libraries in Aura. In short, DRY is not a reason to couple code libraries with similar behaviors; instead, it is a reason to have a single canonical source of knowledge within a system.

Back On The Market!

After a year spent writing my book, working on Aura, speaking at conferences and user groups, advising startups, and proposing new design patterns, I am back on the market.

I’ve been writing PHP code since 1999, and in that time I’ve been everything from a junior developer to a VP of Engineering. If you have a PHP codebase that requires some attention, especially a legacy app that needs to be modernized, I’m your man. I’m also excellent as a leader, mentor, manager, and architect, on small teams and on large ones.

Resume and references available on request. Contact me by email (pmjones88 at gmail) or on Twitter @pmjones if you want to talk!>

UPDATE (Tue 19 Aug): Well that was quick. I’m off the market again, and looking forward to productive efforts with my new employer. My deepest gratitude to everyone who expressed interest; I am truly humbled by the whole experience. Thank you to all.

Soccer, Development, and The Value Of Teamwork

The lesson of soccer is that individual effort will often suffice when things are relatively easy. But in order to surmount the more difficult challenges, you will almost always need reliable teammates of one sort or another.

I assert the same is true in development efforts. A single developer working alone can do good work, but a team of frontend devs, backend devs, devops, and DBAs can do stuff that is truly amazing. Combine your comparative advantages instead of trying to do everything yourself. Via Vox Popoli: Calcio is life.

Action-Domain-Responder, Content Negotiation, and Routers

While talking about Action-Domain-Responder on the Crafting Code Tour, one of the common questions I got was: “Where does content negotiation happen?” My response was always: “Where does it happen in Model-View-Controller?” That opened up a discussion on how content negotiation is a tricky bit that can go in different places, depending on how you want the concerns separated, and is not a problem specific to ADR.

However, I’ve not really been satisfied with that outcome. I enjoyed the question and the discussion, but it never seemed to resolve itself. We were left with this tension between resource conservation and proper separation of concerns. Should negotiation happen in the the Action (Controller), the Domain (Model), or the Responder (View)?

At first it seems like this is clearly a (re)presentation issue, and as such ought to go in the Responder or View. But if the Responder cannot present an acceptable content type for the request, that means we have done a lot of work in the Domain to build objects that will be discarded in favor of a “406 Not Acceptable” response. This is not a good use of our limited resources.

Perhaps the Domain is the place for negotiation? I think we can dismiss this outright. The Domain should not be in charge of returning different presentations of its data.

Finally, we might try negotiation in the Action (Controller). Here we examine the request, and query the Responder to see what content types it can present in responses. (Alternatively, we embed the available content types in both the Action and Responder, duplicating that information somewhat.) If the negotiation fails in the Action, we skip the Domain work and instruct the Responder to return a “406 Not Acceptable”. But that means the Action is now responsible for at least a little bit of the response-building logic. It’s not horrible, but it does not seem as clean as it could be.

After thinking about this for a while, I am beginning to think it is reasonable to perform what I will call a “first filter” on the Accept header at the Front Controller level, specifically in the Router. We already consider the Router as a guard to map incoming requests to appropriate Actions, inspecting the path, HTTP method, and other request information. Inspecting the acceptable types seems a reasonable addition to these elements.

A full content negotiation at the Router level is probably overkill. Really, all the Router needs to know is what content types are provided through particular Route (whether an MVC or ADR one). The matching logic can do a naive check of the Accept request header to see if one of the provided types is present with a non-zero “q” value. If none of the types is present, the Router can move along to the next route, possibly tracking the failure so a Dispatcher can directly invoke a Responder for routing failures. This way, the Router never invokes a non-matching Action, thereby conserving the Domain resources. If the match is successful, the Responder can do the “real” content negotiation work, using an Accept header value passed to it as input from the Action along with the Domain data.

As a proof of concept, I have modified the Aura.Router library to recognize “accept” specifications on the route, and the tests indicate it seems to work just fine.

An Updated Preview Of Aura.Auth

It can be difficult to find a truly standalone, authentication-only library, and Aura.Auth fits that bill.

The library is still under development, but the major pieces are all now in place:

Each layer can handle custom implementations. There are instructions for custom adapters, custom session managers (including session-less authentication), and custom services.

Via An Updated Preview Of Aura.Auth.

Modernizing Legacy PHP: From Service Locator To Dependency Injection

In an earlier article I described how to start moving away from singletons in favor of dependency injection. It occurs to me that the process for moving away from Service Locator is almost exactly the same, except that we use the container outside the class instead of inside it.

Let’s say we have a class that uses a Service Locator. First we examine the class for all uses of the locator. Then, we create constructor parameters for the dependencies it extracts from the locator, and add setter code for those dependencies in the constructor body. For example, we can convert the above Service Locator example classes to these dependency-injected variations:

<?php
class FooClass
{
    protected $db;
    public function __construct(Database $db)
    {
        $this->db = $db;
    }
}

class BarClass
{
    protected $db;
    public function __construct(Database $db)
    {
        $this->db = $db;
    }
}
?>

Finally, any time we instantiate one of these dependency-injected classes, we use the locator outside the class to retrieve the dependencies. We then pass them to the new call for the class. For example:

<?php
// for FooClass
$db = $container->get('db');
$foo = new FooClass($db);

// for BarClass
$db = StaticContainer::get('db');
$bar = new BarClass($db);
?>

Now the class dependencies are explicit and predictable, instead of implicit and unpredictable (i.e., the class might depend on any combination of dependencies hidden inside the container). It is also somewhat easier to build a test, since we only have to build the dependencies themselves, not the container that holds the dependencies.

Afterword

Are you overwhelmed by a legacy PHP application? Have you inherited a spaghetti mess of code? Does it use globals everywhere, so that a fix in one place causes a bug somewhere else? Does every feature addition feel like slogging through a swamp of includes?

It doesn’t have to be that way. “Modernizing Legacy Applications in PHP” gives you step-by-step instructions on how to get your legacy code under control by eliminating globals and separating concerns. Each chapter shows you exactly one task and how to accomplish it, along with common questions related to that task.

When you are done, you will come and go through your code like the wind. Your application will have become autoloaded, dependency injected, unit tested, layer separated, and front controlled. And you will have kept it running the whole time.

Buy the book today!

Aura.SqlQuery 2.0.0 Stable Release

Aura.SqlQuery provides provides a truly independent, fully decoupled package of query-building tools for PHP 5.3 and up. With it, you can use object-oriented techniques to create SELECT, INSERT, UPDATE, and DELETE queries. The package comes with a set of common base query objects, and provides specialized objects for MySQL, PostgreSQL, SQLite, and Microsoft SQL Server.

When we say “truly independent and fully decoupled” we really mean it. The SqlQuery package has no dependencies on any particular database connection system or abstraction layer. For example, you can build a SELECT query, then pass the finished query string to a PDO connection, a mysql connection, or through the database abstraction layer of your choice. This means the package is suitable for any framework or application that needs a query-building mechanism.

Via Aura.SqlQuery v2 Stable Release.