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In daily PHP development, we often need to iterate over arrays or objects. However, due to PHP’s dynamic typing nature, we cannot always guarantee that the passed variable is countable (i.e., an array or implements the Countable interface). Using count() or foreach directly on a non-countable variable may cause errors or warnings, especially when dealing with unstable external data.
To solve this problem, PHP 7.3 introduced the is_countable() function, which checks if a variable is countable before calling count(). This significantly improves code robustness and fault tolerance.
is_countable() is a built-in function available since PHP 7.3+, designed to check whether a variable can be passed to count(). Its function prototype is as follows:
bool is_countable(mixed $value)
The return value is a boolean: true if the variable is an array or implements the Countable interface; otherwise, it returns false.
Suppose we get a set of data from an external API and try to iterate over it:
$data = get_data_from_api();
<p>foreach ($data as $item) {<br>
// Process each item<br>
}<br>
Ideally, $data is an array or an iterable object. But if the API returns null, a string, or a boolean, the above code will trigger warnings or errors.
To avoid this, we can check with is_countable() before iterating:
$data = get_data_from_api();
<p>if (is_countable($data)) {<br>
foreach ($data as $item) {<br>
// Safely process each item<br>
}<br>
} else {<br>
// Optional: log or handle default behavior<br>
error_log("Received non-countable data type.");<br>
}<br>
With this, even if the data returned is null, an integer, or another non-countable type, the program won't crash, enhancing system robustness.
Before PHP 7.3, many developers used is_array() to check countability. While this works in many cases, it cannot detect objects that implement the Countable interface. For example:
class MyCollection implements Countable {
public function count(): int {
return 0;
}
}
<p>$collection = new MyCollection();<br>
At this point:
is_array($collection); // false
is_countable($collection); // true
Therefore, in modern PHP, it is recommended to use is_countable() instead of the combination of is_array() and count().
Always perform type checks on external inputs: especially for database queries, API responses, or other potentially empty structures.
Encapsulate the check logic uniformly: wrap is_countable() checks into a common utility function to keep code clean.
Combine with type hints and static analysis tools: such as PHPStan or Psalm, to further reduce risks caused by unclear types.
is_countable() is a small but powerful tool that makes handling uncertain data structures much easier. Using this function wisely not only prevents runtime errors but also helps write more robust and maintainable PHP applications.
