laravel 如何检查某物是否可数？
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How to check if something is countable?
提问by rap-2-h
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: $a。我不知道那是什么。我想看看我能不能数出来。通常，只有数组，我可以这样做：
if (is_array($a)) {
echo count($a);
}
But some other things are countable. Let's say a Illuminate\Support\Collectionis countable with Laravel:
但其他一些事情是可数的。假设Illuminate\Support\Collection在 Laravel 中a是可数的：
if ($a instanceof \Illuminate\Support\Collection) {
echo count($a);
}
But is there something to do both thing in one (and maybe work with some other countable instances). Something like:
但是，是否可以将两件事合二为一（并且可能与其他一些可数实例一起使用）。就像是：
if (is_countable($a)) {
echo count($a);
}
Does this kind of function exists? Did I miss something?
有这种功能吗？我错过了什么？
回答by Brian Leishman
For previous PHP versions, you can use this
对于以前的 PHP 版本，您可以使用这个
if (is_array($foo) || $foo instanceof Countable) {
return count($foo);
}
or you could also implement a sort of polyfill for that like this
或者你也可以像这样实现一种 polyfill
if (!function_exists('is_countable')) {
function is_countable($c) {
return is_array($c) || $c instanceof Countable;
}
}
Note that this polyfill isn't something that I came up with, but rather pulled directly from the RFC for the new function proposal https://wiki.php.net/rfc/is-countable
请注意，这个 polyfill 不是我想出来的，而是直接从 RFC 中提取的新功能提案https://wiki.php.net/rfc/is-countable
回答by rap-2-h
PHP 7.3
PHP 7.3
According to the documentation, You can use is_countablefunction:
根据文档，您可以使用is_countable功能：
if (is_countable($a)) {
echo count($a);
}
