(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. |
示例 #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)
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) || $var instanceof Countable);
}
}
?>be wary of using is_object($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.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) && $value instanceof Countable);
}
}
?>polyfill:
function is_countable($value) {
return is_array($value)
|| $value instanceof Countable
|| $value instanceof ResourceBundle
|| $value instanceof SimpleXmlElement;
}Polyfill written by arisendrake is not quite good. It return FALSE when checking an Simple XML Node but count() works properly on PHP 7.1 and 7.3.
Better is this one:
<?php
if (version_compare(PHP_VERSION, "7.3") < 0 && !function_exists("is_countable")) {
function is_countable($var): bool
{
return (is_array($var) || is_object($var) || is_iterable($var) || $var instanceof Countable);
}
}
?>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!
?>