如何检查什么东西是可数的?

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:

我有一个var: $a。我不知道是什么。我想看看能不能数一下。通常，只有数组，我可以这样做:

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

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

但是其他的一些事情是可以计算的。让我们假设一个照明\支持收集是可数的与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:

但是，是否有什么事情可以同时做这两件事?喜欢的东西:

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

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

这种函数存在吗?我错过什么了吗?

2 个解决方案

#1

For previous PHP versions, you can use this

对于以前的PHP版本，您可以使用它

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

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

或者你也可以实现一种像这样的多边形

if (!function_exists('is_countable')) {

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

}

#2

PHP 7.3

According to the documentation, You can use is_countable function:

根据文件，可以使用is_countable函数:

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