[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, PHP 8)
count — 変数に含まれるすべての要素、 あるいはオブジェクトに含まれる何かの数を数える
説明
変数に含まれるすべての要素、 あるいはオブジェクトに含まれる何かの数を数えます。
オブジェクトに対して、もし SPL がインストールされている場合、インターフェイス Countable を実装することで count() にフックすることができます。このインターフェイスには 1 つのメソッド Countable::count() があり、count() 関数に対する値を返します。
配列の実装やPHPでの使用法に関する詳細な説明については、マニュアルの 配列のセクションを参照ください。
パラメータ
-
value -
配列あるいは Countable オブジェクト。
-
mode -
オプションの
mode引数がCOUNT_RECURSIVE(または 1) にセットされた場合、count() は再帰的に配列をカウントします。 これは多次元配列の全ての要素をカウントするといった場合に特に有効です。警告count() は、再帰を検出して無限ループを回避するようになっています。 しかしその場合 (配列の中に自分自身が複数回登場する場合) は毎回
E_WARNINGを発行し、期待する結果より大きい数を返します。
返り値
value に含まれる要素の数を返します。
もしパラメータが配列でもなく Countable インターフェイスを
実装したオブジェクトでもない場合、1 が返されます。
ひとつ例外があり、value が null の場合、
0 が返されます。
変更履歴
| バージョン | 説明 |
|---|---|
| 8.0.0 |
value パラメータに不正な型を渡した場合に、
TypeError をスローするようになりました。
|
| 7.2.0 |
value パラメータに不正な型を渡した場合に、
警告を発生させるようになりました。
|
例
例1 count() の例
<?php
$a[0] = 1;
$a[1] = 3;
$a[2] = 5;
var_dump(count($a));
$b[0] = 7;
$b[5] = 9;
$b[10] = 11;
var_dump(count($b));
?>
上の例の出力は以下となります。
int(3) int(3)
例2 Countable|array でない値を渡した場合の count() の例 (悪い例です - 真似しないでね！)
<?php
$b[0] = 7;
$b[5] = 9;
$b[10] = 11;
var_dump(count($b));
var_dump(count(null));
var_dump(count(false));
?>
上の例の出力は以下となります。
int(3) int(0) int(1)
上の例の PHP 7.2 での出力は、このようになります。
int(3) Warning: count(): Parameter must be an array or an object that implements Countable in … on line 12 int(0) Warning: count(): Parameter must be an array or an object that implements Countable in … on line 14 int(1)
上の例の PHP 8 での出力は、このようになります。:
int(3) Fatal error: Uncaught TypeError: count(): Argument #1 ($var) must be of type Countable .. on line 12
例3 再帰的な count() の例
<?php
$food = array('fruits' => array('orange', 'banana', 'apple'),
'veggie' => array('carrot', 'collard', 'pea'));
// 再帰的なカウント
echo count($food, COUNT_RECURSIVE); // output 8
// 通常のカウント
echo count($food); // output 2
?>
参考
- is_array() - 変数が配列かどうかを検査する
- isset() - 変数が宣言されていること、そして null とは異なることを検査する
- empty() - 変数が空であるかどうかを検査する
- strlen() - 文字列の長さを得る
- is_countable() - 引数が、数えられる値かどうかを調べる
add a note
User Contributed Notes 17 notes
onlyranga at gmail dot com ¶
10 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
