On Tue, Nov 28, 2023 at 12:59 AM Sergii Shymko <[email protected]> wrote:
>
> Hi,
>
> Wanted to bring up an inconsistent behavior of callable arguments compared to
> arguments of other types.
> Callable argument cannot have a default value (tested string or array types -
> both are not permitted).
> The same exact value works perfectly fine when passed dynamically, it just
> cannot be specified as a default.
> The workaround is to remove the type annotation which is obviously
> undesirable.
>
> Here’s an example:
> declare(strict_types=1);
> function test(callable $idGenerator = 'session_create_id') {
> $id = $idGenerator();
> // ...
> }
>
> The function/method declaration above produces the following error on all PHP
> versions:
> Fatal error: Cannot use string as default value for parameter $idGenerator of
> type callable in /tmp/preview on line 4
>
> Note that the exact same string argument can be passed without any issue:
> function test(callable $idGenerator) {…}
> test('session_create_id’);
>
> Is there a specific architectural limitation causing this that's
> hard/impossible to overcome?
>
> I’m aware that class properties cannot be annotated with callable - another
> unfortunate limitation.
> Callable is not a real type like other primitive types which causes all these
> inconsistencies, correct?
> Callable properties (separate topic) may be a challenge, but can at least
> argument defaults be supported?
>
> Regards,
> Sergii Shymko
I stopped using "callable" a long time ago. These days I use \Closure
and it works in all the same places (including properties).
If you want to accept a callable string, you need to change the type
to \Closure|string and verify it with `is_callable()`.
> Is there a specific architectural limitation causing this that's
> hard/impossible to overcome?
IIRC, default arguments must be compile-time constant, and this isn't,
apparently:
session_create_id(...)
You can also do something like this:
function hello() {
echo "hi\n";
}
class wrapper {
public function __construct(public \Closure|string $closure) {
is_callable($closure) ?: throw new
InvalidArgumentException('closure must be callable');
}
public function __invoke() {
return ($this->closure)();
}
}
function test(wrapper|Closure $closure = new wrapper('hello')) {
($closure)();
}
test();
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