PHP 7.3: Introduced is_countable() function

PHP 7.2 deprecated quite a lot of functions and buggy use cases. In PHP 7.2, if you call count() on a variable that is not "countable", PHP shows a warning about it. A common fix was to check if the given variable is "countable" before calling count() on it.

A "countable" variable is either an array, or an object of a class that implements \Countable interface. Because there can be a lot of boilerplate code, PHP 7.3 now has a new is_countable() function that returns true if the passed variable is... well... countable.

Polyfill

I have put together a polyfill for is_countable() if you want to use this on pre-PHP 7.3 code.

Here is a simple yet conforming polyfill if you cannot use PHP 7.3 immediately and prefer to not use the package above.

if (!function_exists('is_countable')) {
        function is_countable($var) { 
            return is_array($var) 
                || $var instanceof Countable 
                || $var instanceof ResourceBundle 
                || $var instanceof SimpleXmlElement; 
        }
    }

Backwards compatibility impact

Unless you have declared your own is_countable function, there shouldn't be any issues.

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