is_initialized() helper function

Publish Date: Aug 1 '21

2 5

I'm no fan of (too much) global helper functions, but I feel like is_initalized() is a must! It really should be PHP native, but that's not happening.

This is_initialized() helper is modeled after method_exists(), and others like it, in the sense that it asks for an $object and a $property separately. Reason for this is that we cannot infer the context of a parameter when it is passed like is_initialized($object->parameter). The function would just receive the value.

if (!function_exists('is_initialized')) {
    /**
     * Returns whether a property is initialized with a value.
     * @param string|object $object The class (name), that contains the property.
     * @param string $property The name of the property.
     * @return bool Whether the property is initialized with a value.
     */
    function is_initialized($object, string $property): bool {
        try {
            return (new ReflectionProperty($object, $property))->isInitialized(is_object($object) ? $object : null);
        } catch (ReflectionException $e) {
            return false;
        }
    }
}

Why is this better than `isset()`?

It's not "better" per se, but it makes memoization easier as a value can now also be null. isset() would return false in that case. It kind of depends on your use case.

An example

In this example we use the $service parameter for memoization. The parameter can by either null or a Service instance. In this case, only the first call to getService() would call the container, whereas isset() would call the container multiple times if the value where to be null.

class Controller
{
    private ?Service $service;

    public function getService(): ?Service
    {
        if (!is_initialized($this, 'service')) {
            $this->service = Container::get(Service::class); // either the service, or `null`
        }

        return $this->service;
    }
}

Think you can make this better?

Please let me know if you have an idea on how this function could be even more helpful.

Comments 5 total

William StamAug 6, 2021

Couldn't you just do something like return $this->service ?? Container::get(....):

This->service would be null if it's not "initialised" . ?? Is perfect for that

Doeke NorgAug 7, 2021

Not exactly; although for services a Container is probably optimized enough. So this might not be the best example. I usually do

return $this->service ??= Container::get(...);

to initialize the service, when I am 100% sure the container will return the service.

The "problem" this helper solves is that ?? is the same as isset(), and that will return false for uninitialzed aswel as null. But null is a valid value to initialize a parameter.

So when the value is initalized with null the isset() or ?? check will still trigger the Container::get(...) on subsequent request, while this is_initialized() helper will not. Hope that makes sense.

William StamAug 7, 2021

Isn't using reflection here somewhat adding extra load on the server unnecessarily? Normal execution, stop, check reflection, go on. Sure might be easier for developer but at the cost of runtime? The more your program does the more CPU cycles it consumes. At some point just throwing hardware at it won't be enough. And doing something like this kinda feels like that trap to me.

Not the most liked opinion unfortunately :(

Cool solution tho.

Doeke NorgAug 7, 2021

You're right, performance is something we absolutely have to keep in mind. So I'm glad you point this out.

The Reflection API is actually pretty fast. Of course it adds some extra load, but only on execution time, and even then the differences are minuscule. I ran a phpbench test over 4 situations:

multiple calls on the same instance with isset()
multiple calls on new instances with isset() (every call is a new instance)
multiple calls on the same instance with is_initialized()
multiple calls on new instances with is_initialized() (every call is a new instance)

I ran the test with 10.000 calls, and repeated them 100 times. These are the results:

subject	revs	its	mem_peak	mode	rstdev
benchIsset	10000	100	656.328kb	0.087μs	±6.93%
benchIssetNew	10000	100	656.328kb	0.172μs	±5.01%
benchReflection	10000	100	656.328kb	0.334μs	±4.14%
benchReflectionNew	10000	100	656.344kb	0.433μs	±3.72%

The memory consumption is exactly the same for every situation, except situation 4. But that is not really helpfull with memoization. Even then, the extra memory is negligible.

isset() is definitely faster, but only marginal. You would probably not notice this in your request.

Still, I would only suggest you use this method if you have a memoization situation where the value of your (typed) parameter could also be null. Otherwise, definitely use isset() or ??(=).

William StamAug 7, 2021
This benchmark thing is super super interesting! Thank you!!

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Doeke Norg @doekenorg