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Date: Thu, 15 Aug 2024 17:42:02 +0200
Message-ID: <CABEW5qdVYw3UqiUstV69eKyk1U293ztisFPanR+7kTCFu=9JGw@mail.gmail.com>
Subject: [PHP-DEV] [RFC] On the need of a `is_int_string` ?
To: PHP Internals List <internals@lists.php.net>
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From: misterdeviling@gmail.com (Vincent Langlet)

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Hi,

When string is used as an array key, it's sometimes casted to an int.
As explained in https://www.php.net/manual/en/language.types.array.php:
"Strings containing valid decimal ints, unless the number is preceded by
a + sign, will be cast to the int type. E.g the key "8" will actually be
stored under 8. On the other 08 will not be cast as it isn't a valid
decimal integer."

This behavior cause some issues, especially for static analysis. As an
example https://phpstan.org/r/5a387113-de45-4bef-89af-b6c52adc5f69
vs real life https://3v4l.org/pDkoB

Currently most of static analysis rely on one/many native php functions to
describe types.
PHPStan/Psalm supports a `numeric-string` thanks to the `is_numeric` method.

I don't think there is a native function to know if the key will be casted
to an int. The implementation would be something similar (but certainly
better and in C) to
```
function is_int_string(string $s): bool
{
if (!is_numeric($s)) {
return false;
}

$a[$s] = $s;

return array_keys($a) !== array_values($a);
}
```

Which gives:
is_numeric('08') => true
ctype_digit('08') => true
is_int_string('08') => false

is_numeric('8') => true
ctype_digit('8') => true
is_int_string('8') => true

is_numeric('+8') => true
ctype_digit('+8') => false
is_int_string('+8') => false

is_numeric('8.4') => true
ctype_digit('8.4') => false
is_int_string('8.4') => false

Such method would allow to easily introduce a `int-string` type in static
analysis and the opposite, a `non-int-string` one (cf
https://github.com/phpstan/phpstan/issues/10239#issuecomment-1837571316).

WDYT about adding a `is_int_string` method then ?

Thanks

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<div dir=3D"ltr">Hi,<br><br>When string is used as an array key, it&#39;s s=
ometimes casted to an int.<br>As explained in=C2=A0<a href=3D"https://www.p=
hp.net/manual/en/language.types.array.php">https://www.php.net/manual/en/la=
nguage.types.array.php</a>:<br>&quot;Strings containing valid decimal ints,=
 unless the number is preceded by a=C2=A0+ sign, will be cast to the int ty=
pe. E.g the key &quot;8&quot; will actually be stored under 8. On the other=
 08 will not be cast as it isn&#39;t a valid decimal integer.&quot;<br><br>=
This behavior cause some issues, especially for static analysis. As an exam=
ple=C2=A0<a href=3D"https://phpstan.org/r/5a387113-de45-4bef-89af-b6c52adc5=
f69">https://phpstan.org/r/5a387113-de45-4bef-89af-b6c52adc5f69</a><br>vs r=
eal life=C2=A0<a href=3D"https://3v4l.org/pDkoB">https://3v4l.org/pDkoB</a>=
<br><br>Currently most of static analysis rely on one/many native php funct=
ions to describe types.<br>PHPStan/Psalm supports a `numeric-string` thanks=
 to the `is_numeric` method.<br><br>I don&#39;t think there is a native fun=
ction to know if the key will be casted to an int. The implementation would=
 be something similar (but certainly better and in C) to=C2=A0<br>```<br>fu=
nction is_int_string(string $s): bool<br>{<br>	if (!is_numeric($s)) {<br>		=
return false;<br>	} <br>	<br>	$a[$s] =3D $s;<br>	<br>	return array_keys($a)=
 !=3D=3D array_values($a);<br>}<br>```<br><br>Which gives:<br>is_numeric(&#=
39;08&#39;) =3D&gt; true<br>ctype_digit(&#39;08&#39;) =3D&gt; true<br>is_in=
t_string(&#39;08&#39;) =3D&gt; false<br><br>is_numeric(&#39;8&#39;) =3D&gt;=
 true<br>ctype_digit(&#39;8&#39;) =3D&gt; true<br>is_int_string(&#39;8&#39;=
) =3D&gt; true<br><br>is_numeric(&#39;+8&#39;) =3D&gt; true<br>ctype_digit(=
&#39;+8&#39;) =3D&gt; false<br>is_int_string(&#39;+8&#39;) =3D&gt; false<br=
><br>is_numeric(&#39;8.4&#39;) =3D&gt; true<br>ctype_digit(&#39;8.4&#39;) =
=3D&gt; false<br>is_int_string(&#39;8.4&#39;) =3D&gt; false<br><br>Such met=
hod would allow to easily introduce a `int-string` type in static analysis =
and the opposite, a `non-int-string` one (cf=C2=A0<a href=3D"https://github=
.com/phpstan/phpstan/issues/10239#issuecomment-1837571316">https://github.c=
om/phpstan/phpstan/issues/10239#issuecomment-1837571316</a>).<br><br>WDYT a=
bout adding a `is_int_string` method then ?<br><br>Thanks</div>

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