Uninitialized properties are really useful.
Being skipped in foreach loops and JSON encoded results and other behaviours around uninitialized properties save a lot of time wasted on basic checks and uncaught logical mistakes around null values.
With the introduction of named arguments and promoted constructor properties and read-only classes, it would be great to have the true ability to not specify a value.
Could be handy to allow this in normal functions too (but this it not the main use case and could be disallowed):
Le 3 juin 2025 à 06:22, Bradley Hayes bradley.hayes@tithe.ly a écrit :
Uninitialized properties are really useful.
Being skipped in foreach loops and JSON encoded results and other behaviours around uninitialized properties save a lot of time wasted on basic checks and uncaught logical mistakes around null values.With the introduction of named arguments and promoted constructor properties and read-only classes, it would be great to have the true ability to not specify a value.
``` class DTO { public function __construct( public string $id = uninitialized, public string $name = uninitialized, public null|int $age = uninitialized, ) {} } $dto = new DTO(id: 'someid', age: null); if ($dto->age === null) echo "no age was given\n"; echo $dto->name, PHP_EOL; // triggers the standard access before initialisation error ```EXAMPLE: A graphQL like API that only returns data that was asked for, is serviced by a PHP class that only fetched the data that was asked for and thus the DTO only has assigned values if they were fetched.
(These situations usually way more complex involving multiple SQL joins/filters etc and nested objects/arrays in the return DTO).The DTO object has all the possible values defined on the class for type safety and IDE indexing, but allows the uninitialized error to happen if you try to use data that was never requested.
Uninitialized Errors when directly accessing a property that was not assigned is also desirable as it indicates a logical error instead of thinking the value is null. Null is considered a real value in the database in countless situations and API can assign null to delete a value from an object.
Additionally, since array unpacking now directly maps to named arguments this would also save a ton of mapping code.``` <i>//array unpacking direct from the source </i>$dto = new DTO( ...$sqlData); ```(FYI: SQL is way faster at mapping thousands of values to the naming convention of the class than doing it in php so we do it in SQL. So yes we would directly array unpack an sql result here.)
I have is a discussion on this in github here:
https://github.com/php/php-src/issues/17771The current workaround is to make the constructor take an array as its only parameter and looping over it assigning matching array key values to class properties and ignoring the rest.
This works but breaks indexing and prevents the use of class inheritance because not all the properties can be seen from the same scope forcing every extender of the class to copy paste the constructor code from the parent class.
Hi Bradley,
Originally, null was intended to mean “no value”. Today, null is a value in itself, and there has been a necessity to have something else to encode an uninitialised state, meaning “really, no value”. Although I understand your specific use case, I don’t think that it is good long term design decision to rely on various built-in variations of general “no value” states: maybe tomorrow there will be a request for some “really and truly, no value” state? Instead, I think one should use application-specific states. With enums and union types, it is possible:
enum DTO_status {
case uninitialized;
case deleted;
}
class DTO {
function __construct(
public int|DTO_status $id = DTO_status::uninitialized
, public string|DTO_status $name = DTO_status::uninitialized
, public int|null|DTO_status $age = DTO_status::uninitialized
) { }
}
Or, if you want to rely on the handy error “must not be accessed before initialization” for free, you could also write:
class DTO {
public int $id;
public string $name;
public int|null $age;
function __construct(
int|DTO_status $id = DTO_status::uninitialized
, string|DTO_status $name = DTO_status::uninitialized
, int|null|DTO_status $age = DTO_status::uninitialized
) {
foreach ([ 'id', 'name', 'age' ] as $var) {
if (! ${$var} instanceof DTO_status) {
$this->$var = ${$var};
}
}
}
}
With property hooks, you can support more elaborate things such as $foo->id = DTO_status::deleted, although you cannot (and should not) rely on the built-in “must not be accessed before initialization” error anymore, because you cannot (and are not supposed to) return to the uninitialised state: you have to manually throw the appropriate error in the getter.
—Claude
Hey Claude, i did think of the same thing you proposed and I cover that in the gihub issue I linked to. This doesnt replicate the uninitialized state.
Doing ti with custom classes or enums means now not only are forced to manually check each property everywhere it might be used you also have to write thousands of checks and throw errors across all the constructors of these objects.
When properties have an uninitialized state you remove the need to handle any of this when loops and serializers simply exclude them.
Uninitialized states is already an incredibly useful feature that exists right now.
Im only proposing that we have a way to tell the constructors to ignore the parameter instead of being forced to have array as the only parameter.
I get what you mean about null, but null is serving a different purpose. Its a value that represents nothing, so that you can assign something as nothing.
Uninitialized is not like assigning null to a variable.
// This implementation:
class DTO {
public function __construct(
public string $id = uninitialized,
public string $name = uninitialized,
public null|int $age = uninitialized,
) {}
}
new DTO('some-id');
// Would produce the same result as this one...
class DTO {
public function __construct(array $parameters) {
foreach ($parameters as $key => $value) {
$this->{$key} = $value;
}
}
}
new DTO(['id' => 'some-id']);
Here is another way to think about it, trying to make the arguments optional not have a new value type.
|
- |
Here is another way to think about it, trying to make the arguments optional not have a new value type.
``` Optional arguments currently requires a default value. ``` Assigning values to properties is truly optional but we cant reflect this in the constructor parameters.class DTO { public function __construct( public string $id, optional public string $name, optional public null|int $age, ) {} } new DTO('some-id'); new DTO(...['id' => 'some-id']); // no error for missing keys for named arguments
Hi Bradley,
You can already achieve this, just don’t add those properties to the constructor.
Yes, static analysis tools might complain, but that’s fine if your intention is to leave some properties uninitialized after construction.
The constructor is, by definition, for properties that must be initialized during object creation.
Kind regards,
Faizan