[Editor's note: array at from dot pl had pointed out that count() is a cheap operation; however, there's still the function call overhead.]
If you want to run through large arrays don't use count() function in the loops , its a over head in performance, copy the count() value into a variable and use that value in loops for a better performance.
Eg:
// Bad approach
for($i=0;$i<count($some_arr);$i++)
{
// calculations
}
// Good approach
$arr_length = count($some_arr);
for($i=0;$i<$arr_length;$i++)
{
// calculations
}
count
(PHP 4, PHP 5, PHP 7)
count — 배열의 모든 원소나, 객체의 프로퍼티 수를 셉니다
설명
배열의 모든 원소나, 객체의 프로퍼티 수를 셉니다.
객체는 SPL을 설치했다면, Countable 인터페이스를 가질 경우에 count()를 사용할 수 있습니다. 이 인터페이스는 정확히 하나의 메쏘드 count()을 가지며, count() 함수의 반환값을 반환합니다.
매뉴얼 배열 섹션을 참고하여 배열이 PHP에서 어떻게 구현되고 사용되는지 확인하십시오.
인수
-
var -
배열.
-
mode -
선택적인
mode인수를COUNT_RECURSIVE(또는 1)로 설정하면, count()는 배열을 재귀적으로 셉니다. 이는 다차원 배열의 원소를 셀 경우 유용한 경우가 있습니다.mode기본값은 0입니다. count()는 무한 재귀를 검출하지 못합니다.
반환값
var 안에 있는 원소 수를 반환합니다. 보통
array이며, 다른 자료형은 하나의 요소만 가집니다.
var가 배열이나 Countable
인터페이스를 가진 객체가 아니라면, 1을 반환합니다.
한가지 예외는, var가 NULL일 경우에
0을 반환합니다.
Caution
count()는 설정하지 않은 변수에 대하여 0을 반환하지만, 빈 배열에 대해서도 0을 반환합니다. 변수를 설정했는지 여부는 isset()을 사용하시오.
| 버전 | 설명 |
|---|---|
| 4.2.0 |
선택적인 mode 인수가 추가되었습니다.
|
예제
Example #1 count() 예제
<?php
$a[0] = 1;
$a[1] = 3;
$a[2] = 5;
$result = count ($a);
// $result == 3
$b[0] = 7;
$b[5] = 9;
$b[10] = 11;
$result = count ($b);
// $result == 3;
$result = count(null);
// $result == 0
$result = count(false);
// $result == 1
?>
Example #2 재귀적인 count() 예제
<?php
$food = array( 'fruits' => array('orange', 'banana', 'apple'),
'veggie' => array('carrot', 'collard','pea'));
// 재귀 count
echo count($food,COUNT_RECURSIVE); // 8 출력
// 보통 count
echo count($food); // 2 출력
?>
add a note
User Contributed Notes 17 notes
onlyranga at gmail dot com ¶
9 years ago
lucasfsmartins at gmail dot com ¶
5 years ago
If you are on PHP 7.2+, you need to be aware of "Changelog" and use something like this:
<?php
$countFruits = is_array($countFruits) || $countFruits instanceof Countable ? count($countFruits) : 0;
?>
You can organize your code to ensure that the variable is an array, or you can extend the Countable so that you don't have to do this check.
alexandr at vladykin dot pp dot ru ¶
17 years ago
My function returns the number of elements in array for multidimensional arrays subject to depth of array. (Almost COUNT_RECURSIVE, but you can point on which depth you want to plunge).
<?php
function getArrCount ($arr, $depth=1) {
if (!is_array($arr) || !$depth) return 0;
$res=count($arr);
foreach ($arr as $in_ar)
$res+=getArrCount($in_ar, $depth-1);
return $res;
}
?>
danny at dannymendel dot com ¶
16 years ago
I actually find the following function more useful when it comes to multidimension arrays when you do not want all levels of the array tree.
// $limit is set to the number of recursions
<?php
function count_recursive ($array, $limit) {
$count = 0;
foreach ($array as $id => $_array) {
if (is_array ($_array) && $limit > 0) {
$count += count_recursive ($_array, $limit - 1);
} else {
$count += 1;
}
}
return $count;
}
?>
php_count at cubmd dot com ¶
7 years ago
All the previous recursive count solutions with $depth option would not avoid infinite loops in case the array contains itself more than once.
Here's a working solution:
<?php
/**
* Recursively count elements in an array. Behaves exactly the same as native
* count() function with the $depth option. Meaning it will also add +1 to the
* total count, for the parent element, and not only counting its children.
* @param $arr
* @param int $depth
* @param int $i (internal)
* @return int
*/
public static function countRecursive(&$arr, $depth = 0, $i = 0) {
$i++;
/**
* In case the depth is 0, use the native count function
*/
if (empty($depth)) {
return count($arr, COUNT_RECURSIVE);
}
$count = 0;
/**
* This can occur only the first time when the method is called and $arr is not an array
*/
if (!is_array($arr)) {
return count($arr);
}
// if this key is present, it means you already walked this array
if (isset($arr['__been_here'])) {
return 0;
}
$arr['__been_here'] = true;
foreach ($arr as $key => &$value) {
if ($key !== '__been_here') {
if (is_array($value) && $depth > $i) {
$count += self::countRecursive($value, $depth, $i);
}
$count++;
}
}
// you need to unset it when done because you're working with a reference...
unset($arr['__been_here']);
return $count;
}
?>
jerome dot gds at gmail dot com ¶
4 years ago
to end the debate: count() is the same as empty()
test code below:
results on my computer:
count : double(0.81396999359131)
empty : double(0.81621310710907)
using isset($test[0]) is a bit slower than empty;
test without adding value to the array in function ****Test: still the same.
<?php
function average(array $test)
{
$sum = 0;
foreach($test as $value) {
$sum += $value;
}
return $sum;
}
function countTest(array $test)
{
$i = 0;
while ($i++ < 1000000) {
count($test);
$test["lol$i"] = "teset$i";
}
}
function emptyTest(array $test)
{
$i = 0;
while ($i++ < 1000000) {
empty($test);
$test["lol$i"] = "teset$i";
}
}
$test = [];
$i = 0;
while ($i++ < 20000000) {
$test[] = $i;
}
$j = 10;
$value = $j;
$count = [];
$isEmpty = [];
while ($j--) {
$time = microtime(true);
countTest($test);
$count[] = microtime(true) - $time;
$time = microtime(true);
emptyTest($test);
$isEmpty[] = microtime(true) - $time;
}
var_dump(average($count) / $value);
var_dump(average($isEmpty) / $value);
pied-pierre ¶
8 years ago
A function of one line to find the number of elements that are not arrays, recursively :
function count_elt($array, &$count=0){
foreach($array as $v) if(is_array($v)) count_elt($v,$count); else ++$count;
return $count;
}
Gerd Christian Kunze ¶
10 years ago
Get maxWidth and maxHeight of a two dimensional array..?
Note:
1st dimension = Y (height)
2nd dimension = X (width)
e.g. rows and cols in database result arrays
<?php
$TwoDimensionalArray = array( 0 => array( 'key' => 'value', ...), ... );
?>
So for Y (maxHeight)
<?php
$maxHeight = count( $TwoDimensionalArray )
?>
And for X (maxWidth)
<?php
$maxWidth = max( array_map( 'count', $TwoDimensionalArray ) );
?>
Simple? ;-)
buyatv at gmail dot com ¶
7 years ago
You can not get collect sub array count when there is only one sub array in an array:
$a = array ( array ('a','b','c','d'));
$b = array ( array ('a','b','c','d'), array ('e','f','g','h'));
echo count($a); // 4 NOT 1, expect 1
echo count($b); // 2, expected
Anonymous ¶
4 years ago
For a Non Countable Objects
$count = count($data);
print "Count: $count\n";
Warning: count(): Parameter must be an array or an object that implements Countable in example.php on line 159
#Quick fix is to just cast the non-countable object as an array..
$count = count((array) $data);
print "Count: $count\n";
Count: 250
JumpIfBelow ¶
8 years ago
As I see in many codes, don't use count to iterate through array.
Onlyranga says you could declare a variable to store it before the for loop.
I agree with his/her approach, using count in the test should be used ONLY if you have to count the size of the array for each loop.
You can do it in the for loop too, so you don't have to "search" where the variable is set.
e.g.
<?php
$array = [1, 5, 'element'];
for($i = 0, $c = count($array); $i < $c; $i++)
var_dump($array[$i]);
?>
buyatv at gmail dot com ¶
7 years ago
You can not get collect sub array count when use the key on only one sub array in an array:
$a = array("a"=>"appple", b"=>array('a'=>array(1,2,3),'b'=>array(1,2,3)));
$b = array("a"=>"appple", "b"=>array(array('a'=>array(1,2,3),'b'=>array(1,2,3)), array(1,2,3),'b'=>array(1,2,3)), array('a'=>array(1,2,3),'b'=>array(1,2,3))));
echo count($a['b']); // 2 NOT 1, expect 1
echo count($b['b']); // 3, expected
vojtaripa at gmail dot com ¶
3 years ago
To get the count of the inner array you can do something like:
$inner_count = count($array[0]);
echo ($inner_count);
ThisIsNotImportant ¶
8 years ago
About 2d arrays, you have many way to count elements :
<?php
$MyArray = array ( array(1,2,3),
1,
'a',
array('a','b','c','d') );
// All elements
echo count($MyArray ,COUNT_RECURSIVE); // output 11 (9 values + 2 arrays)
// First level elements
echo count($MyArray ); // output 4 (2 values+ 2 arrays)
// Both level values, but only values
echo(array_sum(array_map('count',$MyArray ))); //output 9 (9 values)
// Only second level values
echo (count($MyArray ,COUNT_RECURSIVE)-count($MyArray )); //output 7 ((all elements) - (first elements))
?>
flavioaugusto dot br at gmail dot com ¶
5 years ago
Criada para contar quantos níveis um array multidimensional possui.
function count_multiLevel($matrix, $_LEVEL = 0){
/* Variáveis de recursão */
$_COUNT = $_LEVEL;
/* Verifica se o ARRAY foi instanciado */
if (is_setVar($matrix)){
/* Verifica se a variável é um ARRAY */
if(is_array($matrix)){
/* Loop de elementos da matriz*/
foreach ($matrix as $elements => $value) {
/* Auxiliar para verificação posterior */
$_AUX = $_COUNT;
/* Verifiando os Nós */
if (is_array($matrix[$elements])) {
$_COUNT = count_multiLevel($matrix[$elements], $_LEVEL+1);
}
/* Cereja do bolo */
if($_AUX > $_COUNT)
$_COUNT = $_AUX;
}
/* Retorn do resultado da operação */
return $_COUNT;
}else{
/* Em casos que o valor passado não seja uma matriz/array */
return -1;
}
}
}
max at schimmelmann dot org ¶
4 years ago
In special situations you might only want to count the first level of the array to figure out how many entries you have, when they have N more key-value-pairs.
<?php
$data = [
'a' => [
'bla1' => [
0 => 'asdf',
1 => 'asdf',
2 => 'asdf',
],
'bla2' => [
0 => 'asdf',
1 => 'asdf',
2 => 'asdf',
],
'bla3' => [
0 => 'asdf',
1 => 'asdf',
2 => 'asdf',
],
'bla4' => [
0 => 'asdf',
1 => 'asdf',
2 => 'asdf',
],
],
'b' => [
'bla1' => [
0 => 'asdf',
1 => 'asdf',
2 => 'asdf',
],
'bla2' => [
0 => 'asdf',
1 => 'asdf',
2 => 'asdf',
],
],
'c' => [
'bla1' => [
0 => 'asdf',
1 => 'asdf',
2 => 'asdf',
]
]
];
$count = array_sum(array_values(array_map('count', $data)));
// will return int(7)
var_dump($count);
// will return 31
var_dump(count($data, 1));
?>
XavDeb ¶
4 years ago
If you want to know the sub-array containing the MAX NUMBER of values in a 3 dimensions array, here is a try (maybe not the nicest way, but it works):
function how_big_is_the_biggest_sub ($array) {
// we parse the 1st level
foreach ($array AS $key => $array_lvl2) {
//within level 2, we count the 3d levels max
$lvl2_nb = array_map( 'count', $array_lvl2) ;
$max_nb = max($lvl2_nb);
// we store the matching keys, it might be usefull
$max_key = array_search($max_nb, $lvl2_nb);
$max_nb_all[$max_key.'|'.$key] = $max_nb;
}
// now we want the max from all levels 2, so one more time
$real_max = max($max_nb_all);
$real_max_key = array_search($real_max, $max_nb_all);
list($real_max_key2, $real_max_key1) = explode('|', $real_max_key);
// preparing result
$biggest_sub['max'] = $real_max;
$biggest_sub['key1'] = $real_max_key1;
$biggest_sub['key2'] = $real_max_key2;
return $biggest_sub;
}
/*
$cat_poids_max['M']['Juniors'][] = 55;
$cat_poids_max['M']['Juniors'][] = 61;
$cat_poids_max['M']['Juniors'][] = 68;
$cat_poids_max['M']['Juniors'][] = 76;
$cat_poids_max['M']['Juniors'][] = 100;
$cat_poids_max['M']['Seniors'][] = 55;
$cat_poids_max['M']['Seniors'][] = 60;
$cat_poids_max['M']['Seniors'][] = 67;
$cat_poids_max['M']['Seniors'][] = 75;
$cat_poids_max['M']['Seniors'][] = 84;
$cat_poids_max['M']['Seniors'][] = 90;
$cat_poids_max['M']['Seniors'][] = 100;
//....
$cat_poids_max['F']['Juniors'][] = 52;
$cat_poids_max['F']['Juniors'][] = 65;
$cat_poids_max['F']['Juniors'][] = 74;
$cat_poids_max['F']['Juniors'][] = 100;
$cat_poids_max['F']['Seniors'][] = 62;
$cat_poids_max['F']['Seniors'][] = 67;
$cat_poids_max['F']['Seniors'][] = 78;
$cat_poids_max['F']['Seniors'][] = 86;
$cat_poids_max['F']['Seniors'][] = 100;
*/
$biggest_sub = how_big_is_the_biggest_sub($cat_poids_max);
echo "<li> ".$biggest_sub['key1']." ==> ".$biggest_sub['key2']." ==> ".$biggest_sub['max']; // displays : M ==> Seniors ==> 7
