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Date: Sat, 15 Oct 2022 16:12:35 +0200
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To: Gianni Gentile <g.gentile@parentesigraffe.com>, internals@lists.php.net
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Subject: Re: [PHP-DEV] Casting array to any class
From: thomas@nunninger.info (Thomas Nunninger)

Hi,

Am 15.10.22 um 13:18 schrieb Gianni Gentile:
> Hi,
> 
> in my every day experience, using custom DTO classes and different API, 
> I often write code to instantiate my objects from associative arrays.
> 
> What are your thoughts on introduce the `(AnyType)` cast to instantiate 
> objects from associative array (or object properties also)?
> 
> In my proposal, if AnyType implements __set_state(), casting should be 
> syntactic sugar for:
> 
>      AnyType::_set_state((array) $data)
> 
> just for (useless) example, consider DateTime or DateTimeImmutable (both 
> have __set_state() implementation); when applied to objects of that 
> type, we can write:
> 
>      $dt = new DateTime();
> 
>      $dtArray = (array) $dt; // 3 elements array
> 
>      $copyOfDt = (DateTime) $dtArray; // or simply $copyOfDt = 
> (DateTime) $dt;
> 
> In case AnyType does not implements __set_state(), casting should create 
> a new instance, assigning values to properties, taken from array values 
> with corresponding key (in a similar way class objects are created when 
> row is fetched from database specifying PDO_FETCH_CLASS) eventually 
> invoking __set() magic method for properties not declared;
> 
> In this scenario,
> 
>      (object) ['one' => 1, 'two' => 2]
> 
> and
> 
>      (StdClass) ['one' => 1, 'two' => 2]
> 
> do exactly the same work.
> 
> 
> Reasons:
> 
> - clear code
> 
> - array to object conversion (casting) would be the simmetrical 
> counterpart of object to array conversion


I see your use case and I often have similar needs. Some thoughts:

* Are there any restrictions regarding the matching of array keys and 
the class attributes? What if there are additional keys in the array 
that do not have corresponding attributes? What if there are some 
attributes in the class that do not exist in the array?

* Can I forbid a class to be created by casting from an array? When I 
think about domain entities/aggregates, such a casting would allow to 
create an invalid state of the object without any checks. (Okay, we have 
similar issues when recreating them from a database via some ORM.)

BTW:

<?php declare(strict_types=1);

class A
{
     private string $myPrivate = 'private';
     protected string $myProtected = 'protected';
     public string $myPublic = 'public';
}

$a = new A();

var_dump((array) $a);

?>

Will dump with modified array keys:

/home/thomas/test.php:12:
array(3) {
   '\0A\0myPrivate' =>
   string(7) "private"
   '\0*\0myProtected' =>
   string(9) "protected"
   'myPublic' =>
   string(6) "public"
}

So it's not as symmetric as intended.

Regards
Thomas