Countable::count

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

Countable::count统计对象的元素个数

说明

public Countable::count(): int

count()value 是实现 Countable 的对象时,会执行此方法。

参数

此函数没有参数。

返回值

int 形式的自定义计数。

示例

示例 #1 Countable::count() 示例

<?php

class Counter implements Countable
{
private
$count = 0;

public function
count(): int
{
return ++
$this->count;
}
}

$counter = new Counter;

for (
$i = 0; $i < 10; ++$i) {
echo
"I have been count()ed " . count($counter) . " times\n";
}

?>

以上示例的输出类似于:

I have been count()ed 1 times
I have been count()ed 2 times
I have been count()ed 3 times
I have been count()ed 4 times
I have been count()ed 5 times
I have been count()ed 6 times
I have been count()ed 7 times
I have been count()ed 8 times
I have been count()ed 9 times
I have been count()ed 10 times
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用户贡献的备注 2 notes

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13
SenseException
11 years ago
Even though Countable::count method is called when the object implementing Countable is used in count() function, the second parameter of count, $mode, has no influence to your class method.

$mode is not passed to Countable::count:

<?php

class Foo implements Countable
{
public function
count()
{
var_dump(func_get_args());
return
1;
}
}

count(new Foo(), COUNT_RECURSIVE);

?>

var_dump output:

array(0) {
}
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1
moris at moris dot org dot ua
15 days ago
First, the commonly referenced example of Countable is somewhat misleading from an OOP perspective, as it unintentionally violates some key principles. While it demonstrates the concept of Countable, it does so in a way that could cause confusion.

According to the Countable interface:

<?php
/**
* Count elements of an object
* @link https://php.net/manual/en/countable.count.php
* @return int<0,max> The custom count as an integer.
* <p>
* The return value is cast to an integer.
* </p>
*/
#[TentativeType]
public function
count(): int;
?>

This means that the `count()` method should not modify the state of an object—it should simply return an integer value, aligning with SOLID principles.

A proper OOP approach would be:

<?php
class Counter implements Countable
{
private
$count = 0;

// Returns the item count of the object
public function count(): int
{
return
$this->count;
}

public function
increment(): void
{
$this->count++;
}
}

$counter = new Counter;

for (
$i = 0; $i < 10; ++$i) {
$counter->increment();
echo
"I have been incremented " . count($counter) . " times\n";
}
?>

Here, count() correctly returns the number of elements, while increment() is responsible for modifying the state of the object.

A separate discussion can be had about whether to use count($object) or $object->count(), but that’s a different topic.
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