How to check if something is countable?

Question

I have a var: $a. I don't know what it is. I want to check if I can count it. Usually, with only array, I can do this:

if (is_array($a)) {
    echo count($a);
}

But some other things are countable. Let's say a Illuminate\Support\Collection is countable with Laravel:

if ($a instanceof \Illuminate\Support\Collection) {
    echo count($a);
}

But is there something to do both thing in one (and maybe work with some other countable instances). Something like:

if (is_countable($a)) {
    echo count($a);
}

Does this kind of function exists? Did I miss something?

Circumfluent

maybe #12346979 ? with $var instanceof Countable – Patience

@Scuzzy's way is a good start and maybe is worth also trying to see if is traversable: php.net/manual/en/class.traversable.php – Settera

php.net/manual/en/function.count.php – Jake

Good news. It is looking like PHP 7.3 is aiming to have a built in function for this wiki.php.net/rfc/is-countable – Snowslide

Answer 1

PHP 7.3

According to the documentation, You can use is_countable function:

if (is_countable($a)) {
    echo count($a);
}

Circumfluent

That's for a version of PHP that isn't released yet :D – Branton

PHP 7.3 Alpha 1 is now released. Please also note: PHP 7.3 SHOULD NOT be used in production. Please wait for Production Ready version to save yourself for the hassle. – Footgear

We're at 7.4 now, so this answer is now more than acceptable. – Ridicule

Answer 2

For previous PHP versions, you can use this

if (is_array($foo) || $foo instanceof Countable) {
    return count($foo);
}

or you could also implement a sort of polyfill for that like this

if (!function_exists('is_countable')) {

    function is_countable($c) {
        return is_array($c) || $c instanceof Countable;
    }

}

---

Note that this polyfill isn't something that I came up with, but rather pulled directly from the RFC for the new function proposal https://wiki.php.net/rfc/is-countable

Hysteric