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Date: Fri, 17 May 2024 23:40:19 +0200
Message-ID: <CAAX=eQNH0xyoRkMDThvG_aNS5Hub3tFD52v4PY3OZKT_zWaMmg@mail.gmail.com>
Subject: [PHP-DEV] [DISCUSSION] Checking uninitialized class properties
To: internals@lists.php.net
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From: cardamoneluigi@gmail.com (Luigi Cardamone)

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Hello Internals,
during last PHPDay in Verona I discussed this topic with some of
you and it was suggested to me to send an email here.

Here is an example to describe my problem. Imagine a simple
DTO like this:

class MyDTO{
    public ?int $propA;
    public ?int $propB;
}

Imagine that a Form processor or a generic mapper fill some of
these fields with a null value:

$dto = new MyDTO();
$dto->propA = null;

Sometimes we use DTOs to handle PATCH requests and not all
the properties are mapped with a value. In a scenario like this,
"null" is often a valid value.

At this point, I need a way to find if a property was initialized or
not but unfortunately "isset" is not a solution. When I write:

echo isset($dto->propA) ? 'init' : 'not-init';

I get "not-init" since isset returns true only if the variable is set
and different from null.

Full example: https://3v4l.org/4cCj0

Is the language missing a clean way to check if a property is
initialized or not? Is there any solution to this problem?

The only alternative is using reflection but I need to pass the
property name as a string losing static analysis.
Proposing a new language syntax like
"is_initialized($dto->propA)" can be an interesting solution?

Thank you in advance.

Luigi Cardamone
Backend developer
Italy

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<div dir=3D"ltr">Hello Internals,<br>during last PHPDay in Verona I discuss=
ed this topic with some of<br>you and it was suggested to me to send an ema=
il here.<br><br>Here is an example to describe my problem. Imagine a simple=
<br>DTO like this:<br><br>class MyDTO{<br>=C2=A0 =C2=A0 public ?int $propA;=
<br>=C2=A0 =C2=A0 public ?int $propB;<br>}<br><br>Imagine that a Form proce=
ssor or a generic mapper fill some of<br>these fields with a null value:<br=
><br>$dto =3D new MyDTO();<br>$dto-&gt;propA =3D null;<br><br>Sometimes we =
use DTOs to handle PATCH requests and not all<br>the properties are mapped =
with a value. In a scenario like this,<br>&quot;null&quot; is often a valid=
 value.<br><br>At this point, I need a way to find if a property was initia=
lized or<br>not but unfortunately &quot;isset&quot; is not a solution. When=
 I write:<br><br>echo isset($dto-&gt;propA) ? &#39;init&#39; : &#39;not-ini=
t&#39;;<br><br>I get &quot;not-init&quot; since isset returns true only if =
the variable is set<br>and different from null.<br><br>Full example: <a hre=
f=3D"https://3v4l.org/4cCj0">https://3v4l.org/4cCj0</a><br><br>Is the langu=
age missing a clean way to check if a property is<br>initialized or not? Is=
 there any solution to this problem?<br><br>The only alternative is using r=
eflection but I need to pass the<br>property name as a string losing static=
 analysis.<br>Proposing a new language syntax like<br>&quot;is_initialized(=
$dto-&gt;propA)&quot; can be an interesting solution?<br><br>Thank you in a=
dvance.<br><br>Luigi Cardamone<br>Backend developer<br>Italy</div>

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