(PHP 7 >= 7.3.0, PHP 8)
is_countable — Verify that the contents of a variable is a countable value
Verify that the contents of a variable is an array or an object implementing Countable
valueThe value to check
Returns true if value is countable, false
otherwise.
| 版本 | 说明 |
|---|---|
| 7.3.0 | is_countable() has been added. |
Example #1 is_countable() examples
<?php
var_dump(is_countable([1, 2, 3])); // bool(true)
var_dump(is_countable(new ArrayIterator(['foo', 'bar', 'baz']))); // bool(true)
var_dump(is_countable(new ArrayIterator())); // bool(true)
var_dump(is_countable(new stdClass())); // bool(false)
Note: if is_countable() return true is does not guarantee that the it can be calculated recursively and correctly:
<?php
$iterator = new ArrayIterator(['one', 'two', new ArrayIterator(['three', 'four'])]);
var_dump(is_countable($iterator), count($iterator, COUNT_RECURSIVE));
// return TRUE and 3!
?>
Fixed polyfill:
<?php
if (! function_exists('is_countable')) {
/**
* @param mixed $value The value to check
* @return bool
*/
function is_countable($value): bool
{
return is_array($value) || (is_object($value) && $value instanceof Countable);
}
}
?>
be wary of using is_object($var) and assuming that the object has implemented Countable. Not all objects are countable directly with count().
Note that a polyfill for this method is also provided by the symfony/polyfill project.
Polyfill written by arisendrake is not quite good. It return FALSE when checking an Simple XML Node but count() works properly on PHP 7.1 and 7.3.
Better is this one:
<?php
if (version_compare(PHP_VERSION, "7.3") < 0 && !function_exists("is_countable")) {
function is_countable($var): bool
{
return (is_array($var) || is_object($var) || is_iterable($var) || $var instanceof Countable);
}
}
?>
If you are unable to upgrade to PHP 7.3 (not released at the time of writing), you can use this simple polyfill:
<?php
if (!function_exists('is_countable')) {
function is_countable($var) {
return (is_array($var) || $var instanceof Countable);
}
}
?>