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Date: Wed, 22 Oct 2014 14:35:45 +0200
CC: Andrea Faulds <ajf@ajf.me>,
 PHP Internals <internals@lists.php.net>
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To: Dmitry Stogov <dmitry@zend.com>
Subject: Re: [PHP-DEV] [RFC] Safe Casting Functions
From: bobwei9@hotmail.com (Weinand Bob)

So, what exactly changes here if we have a second parameter or just =
return null by default?
It doesn=E2=80=99t make any difference, it=E2=80=99s just another way to =
write it:

to_int($a, $default)
or
to_int($a) ?? $default

Also, if you want exceptions, you always can wrap a userland function =
around it =E2=80=94 but I=E2=80=99d rather not wrap an userland function =
around something throwing an exception=E2=80=A6 inefficient and weird.

Thanks,
Bob

> Am 22.10.2014 um 12:27 schrieb Dmitry Stogov <dmitry@zend.com>:
>=20
> "null" or "false" return value would make these functions not really
> useful, because they won't guarantee to return desired type.
>=20
> printf("%d\n", to_int("abcd")); // will print 0
>=20
> The only reliable option to support wrong input is exceptions.
> On the  other hand, exceptions maybe difficult to use or inefficient.
> We may avoid exceptions throwing, if provide a default value:
>=20
> function to_int(mixed $a , int $default_value =3D null): int;
> function to_double(mixed $a , double $default_value =3D null): double;
> function to_string(mixed $a, string $default_value =3D null): string;
>=20
> Thanks. Dmitry.
>=20
> On Wed, Oct 22, 2014 at 12:37 PM, Bob Weinand <bobwei9@hotmail.com> =
wrote:
>=20
>> I know we have that already discussed a lot now, but I=E2=80=99d like =
to expose my
>> points on the return value here:
>>=20
>> I imagine code like (supposing that we ever will have scalar =
typehints):
>>=20
>> function acceptsInt (int $i =3D null) {
>>    if ($i =3D=3D=3D null) {
>>        $i =3D 2 /* default value */;
>>    }
>>    /* do something with $i */
>> }
>>=20
>> When we return false:
>> acceptInt(($tmp =3D to_int($_GET["userinput"])) =3D=3D=3D false ? =
null : $tmp);
>>=20
>> When we throw an exception:
>> try {
>>    acceptInt(to_int($_GET["userinput"]));
>> } catch (CastingException $e) {
>>    acceptInt(null);
>> }
>>=20
>> When we just return null:
>> acceptInt(to_int($_GET["userinput"]));
>>=20
>> Also, when we want to pass a default value defined outside of the
>> function, it=E2=80=99s a lot easier now with the coalesce operator:
>> acceptInt(to_int($_GET["userinput=E2=80=9C]) ?? 2 /* default value =
*/);
>>=20
>>=20
>> Also, independently of possible scalar typehints:
>>=20
>> Generally exceptions are also a bad idea as the casts probably will =
be
>> used on external input and exceptions are **not** a way to handle =
malformed
>> user input. Really not.
>> Furthermore, false is a bad idea in the same sense (if we get scalar =
type
>> hints once), because people then might just catch the =
EngineException=E2=80=A6
>>=20
>> Also, null means "no value"; that=E2=80=99s exactly what we need. If =
the
>> to_{type}() functions cannot return a meaningful value, just return =
"no
>> value", that means null. And not false, which is a real value.
>>=20
>> That=E2=80=99s why I strongly feel that null is the only true thing =
to return here.
>>=20
>> Thanks,
>> Bob
>>=20
>>> Am 21.10.2014 um 00:57 schrieb Andrea Faulds <ajf@ajf.me>:
>>>=20
>>> Good evening,
>>>=20
>>> I am presenting a new RFC to add a set of three functions to do
>> validated casts for scalar types:
>>>=20
>>> https://wiki.php.net/rfc/safe_cast
>>>=20
>>> Please read it.
>>>=20
>>> Thanks!
>>> --
>>> Andrea Faulds
>>> http://ajf.me/