FutureProgrammingTechnologyWeb Development

and now for something completely different

In the our 20-odd years with PHP, there have always been people attempting to work a step or two ahead of where the language was at the time. Working with PHP4 in the early 2000s, when a very elementary Java-derived object model was grafted on the language, people attempted to write proper Java without the guardrails. Objects are the sort of thing that, if your language doesn’t give you, you will probably try to invent, as people before that with PHP3.

PHP5 brought the gradual strengthening of the language’s object model, as well as dynamic “magic methods” which people ran wild with in the late 2000s, stretching things every which way. By the early 2010s the ecosystem had sobered up and begun to build serious structures around it. The language got a proper package manager in Composer, and in playing by a set of community-established conventions, one could draw upon vast resources for free. Many of us did, and over the lifespan of PHP5, the language completed a transformation from its hobbyist origins to something more enterprise-worthy. This was only aided by the widespread shift to cloud-centric computing, which PHP — stateless by nature — was uniquely equipped to handle.

PHP: The Next Generation

PHP7 came at an opportune time in the mid-2010s. Apparent competition from Facebook’s PHP-based hacklang seemed to kick the release schedule for PHP5’s sequel into high gear, amidst worries that a competing, partially-compatible offshoot would fragment the ecosystem. The internals team, which typically ties major version jumps (3 to 4, 4 to 5, 5 to . . . 7) to significant engine improvements, did not disappoint. Version 7 arrived with huge speed improvements (5x, by many counts) and set about, over the lifespan of the 7.x line, finishing the task of strengthening the language’s guardrails. The end result took much of the wind out of hacklang’s sails and, though it continues as a part of facebook’s internal toolset, the feared splintering of the community did not arrive.

Now, as we await the arrival of PHP Next Generation — Version 8 — in the closing months of 2020, let’s look at how we’ve continued to work at the margins in our time with PHP 7, and how we can expect to see our visions realized in future PHP.

make it so

Building a more reflective environment

Beyond the speed boost, PHP greatly strengthened the type system, once considered a critical weakness of the language. Once a weakly typed language, its modern incarnations are more accurately gradually typed — that is to say, while you can still work in a fast and loose way as before, structure and boundary may be introduced as the lines become more defined.

Through external tools, through linters and validation, structure and boundary may be enforced on a project level. The language may be wielded in a way acceptable to the enterprise, without losing the dynamism, flexibility and lightness of weight that characterize a scripting language.

If PHP is the best of both worlds, it’s the hardening of its type system that has brought it there, and it’s around its type system that our work has revolved.

class Before {
protected $database;
public function getUser($id, $password);
}
class After {
protected $database;
public function getUser(int $id, string $age): User;
}

Before is an example of a method signature, PHP5-style. We can infer that $id is probably a number, and $password is probably a string of text. getUser probably returns a user record. These are all reasonable assumptions, but there’s no actual indication of this, and certainly no enforcement. What happens if you pass in a textual ID and a numeric password, or trick it to return something other than a user record? And putting aside everything that could go wrong at runtime, there’s little usable information here for an IDE to provide hinting as you work.

(In the months before PHP7 was announced, our team had a working model that looked an awful lot like After, running entirely on plain-vanilla PHP 5.4. We stopped work on it at that point, and the less we say about how we did it, the better.)

After, using the syntactic enhancements of PHP7, is replete with useful information for automated tools and human readers, and establishes clear boundaries for runtime operation. Try feeding in the wrong values, or coaxing out a bad result. The engine itself will refuse.

So what did people do before 2015? Labour with blind IDEs, unable to analyze their code? No, the PHP community did what it does in the face of adversity and established sensible community standards. Deriving from the Javadoc format, DocBlocks became a standard way of expressing the intent of a program.

class Annotated {
/** @var Connection */
protected $database;
/**
* Retrieve a user from the database.
* @param int $id
* @param string $password
* @throws UserNotFoundException
* @returns User
*/
public function getUser($id, $password);
}

In this way, people were pretending that PHP was well-typed long before it was. Now, these specifications are suggestions, not rules: the language does not register them and will not enforce them at runtime. But they provide a standard way to provide a wealth of metadata beyond what the type system can adequately capture, even now. (Referring back to the After diagram, you’ll notice that this diagram contains more information. PHP 7.0 was incapable of attaching type information to $database, and it doesn’t specify possible error states.)

So on our side we’ve got a consistently improving type system and well-defined documentation format with broad community support. We’ve got powerful Reflection capabilities built in to the language — that is, programs can read their own blueprint, make decisions based on their own structure. All this within a language with a history of dynamism and “magic” undefined conditions.
So let’s look at one way in which we worked past a shortcoming of PHP, and had the opportunity to loop back once the language caught up.

Typed Properties in PHP 7

Let’s dwell for a second or two on a fragment of the last two code samples, to see a shortcoming of PHP 7.0 as it initially shipped.

class After {
protected $database;
}
class Annotated {
/** @var Connection */
protected $database;
}

In contrast to methods, class properties such as the $database are as weakly-typed as ever before. Within a class, it’s the honour system. If you were to make $database public rather than protected, you’d be merely trusting the rest of your system not to pass in a bad value, and you’re telling the rest of system nothing (except by way of commentary) of its intended content.

Meanwhile, our team is building a framework around a Dependency Injection container, and this is a crucial bit of missing information for us as we attempt to analyze and fulfill the needs of a class.
But since we have metadata available in another way, we end up with something like this:

class ExampleController {
/**
* @var UserEntity
* @Inject(required=true)
*/
protected $user;
}

No, not the prettiest. We earnestly wished, at the time, that we could express property types like this:

class ExampleController {
protected UserEntity $user;
}

and Annotations like this, such as in Java:

class ExampleController {
@Inject(required=true)
protected $user;
}

but we continue to build our system as if the language had those functionalities, without our own implementations as a stopgap. In each case, we were expecting the language to go that way eventually, though we couldn’t say for certain any timeframe.

Sure enough, as development of PHP 7.x continued and initial shortcomings were resolved one by one, we got one item checked off our wishlist with PHP 7.4. Typed Properties now allowed the above to be slimmed down to:

class ExampleController {
/** @Inject(required=true) */
protected UserEntity $user;
}

Furthermore, the properly typed property doesn’t function just as a suggestion for the dependency system to interpret and fulfill. Another guardrail, formally in place, and we began supporting this method within our framework immediately. But its addition didn’t invalidate the old method. @var annotations remain valid and will remain so indefinitely.
But speaking of annotations…

Annotations in PHP 8

This is a bit of a “stop the presses” moment, as I had already written how this remains a long-running, major item on our wishlist. How I had followed various RFCs over the past decade, hopeful for each of them, resigned to the reality that it might never be accepted.

Our half-way implementation might be all we ever had, and that was okay. Then, with my press date looming, this lands in my inbox:

i just closed the vote. [Attributes v2](https://wiki.php.net/rfc/attributes_v2) was accepted with 51 yay, 1 nay. The selected syntax will be <<Attribute>>.

Thank you everyone for participating in the discussion and vote!

I was more than glad to tear up that draft, and I’ll be glad to see DocBlock annotations become an optional feature as code like this becomes the norm:

class ExampleController {
<<Inject>>
protected UserEntity $user;
}

Yet, even as the language has caught up with our intentions and we’ve adapted our course accordingly, functionality has remained consistent throughout. The language gave us enough rope to mock-up both features to the degree that we didn’t feel impoverished in their absence, and were able to pivot effortlessly when both were introduced.

It remains to be seen what aspect of PHP 9 we end up building, but we look forward to discovery.

There are many reasons to be excited for PHP 8!

Annotations — er, Attributes — are a definite favourite here, but a major PHP release is a big deal and we’ll be here in future weeks to go through them all.