iterator_count

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

iterator_count — 计算迭代器中元素的个数

说明

iterator_count ( Traversable $iterator ) : int

计算迭代器中的元素个数。

参数

iterator: 要计数的迭代器。

返回值

迭代器iterator中的元素个数。

范例

Example #1 iterator_count() example


<?php
$iterator = new ArrayIterator(array('recipe'=>'pancakes', 'egg', 'milk', 'flour'));
var_dump(iterator_count($iterator));
?>

以上例程会输出：

int(4)

User Contributed Notes

oleksii dot bulba at gmail dot com 01-Sep-2021 07:20


Be aware that counting over NoRewindIterator will make items unavailable:



<?php



$iterator = new ArrayIterator(['recipe'=>'pancakes', 'egg', 'milk', 'flour']);

$iterator = new NoRewindIterator($iterator);



var_dump($iterator->current());

var_dump(iterator_count($iterator));

var_dump($iterator->current());

$iterator->rewind(); // Does not work because it's NoRewindIterator

var_dump($iterator->current());

var_dump(iterator_count($iterator));



?>



Output:



<?php



/*

string(8) "pancakes"

int(4)

NULL

NULL

*/

int(0)



?>

info at ensostudio dot ru 16-Oct-2020 12:31


Safe using:

<?php

$cnt = iterator_count(clone $iterator);

?>

fractile81 at gmail dot com 05-Jun-2020 02:33


After using this function, the traversable's pointer will point at the end.  Examples 2 and 3 highlight this using code.



This means that when you call iterator_count($foo)...

- Before a foreach-loop on $foo, the loop will not execute because it's already at the end.  Calling $foo->rewind() will reset the traversable to the beginning.

- Inside a foreach-loop on $foo, the loop will complete the current iteration and not repeat.  Something like $foo->seek($i) can be used to reset the pointer, where $i contains the pointer's value prior to counting.