[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
}
PHP - Manual: count
2024-11-15
说明
用于数组时，统计数组中元素的数量；用于实现了 Countable 接口的对象时，返回 Countable::count() 方法的返回值。
参数
-
value -
数组或者 Countable 对象。
-
mode -
如果可选的
mode参数设为COUNT_RECURSIVE（或 1），count() 将递归地对数组计数。对计算多维数组的所有单元尤其有用。警告count() 能检测递归来避免无限循环，但每次出现时会产生
E_WARNING错误 （如果 array 不止一次包含了自身）并返回大于预期的统计数字。
返回值
返回 value 中的元素的数量。在 PHP 8.0.0
之前，如果参数既不是数组也不是实现了 Countable 接口的对象，将返回
1。当 value 为 null 时返回
0。
更新日志
| 版本 | 说明 |
|---|---|
| 8.0.0 |
当 value 参数传入了无效的 countable 类型，
count() 现在会抛出 TypeError。
|
| 7.2.0 |
当 value 参数传入了无效的 countable 类型，
count() 现在会产生警告。
|
范例
示例 #1 count() 例子
<?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));
?>
以上例程会输出：
int(3) int(3)
示例 #2 count() 非 Countable|array 的例子 （这是个反例，请勿模仿）
<?php
$b[0] = 7;
$b[5] = 9;
$b[10] = 11;
var_dump(count($b));
var_dump(count(null));
var_dump(count(false));
?>
以上例程会输出：
int(3) int(0) int(1)
Output of the above example in PHP 7.2:
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)
以上例程在 PHP 8 中的输出：
int(3) Fatal error: Uncaught TypeError: count(): Argument #1 ($var) must be of type Countable .. on line 12
示例 #3 递归 count() 例子
<?php
$food = array('fruits' => array('orange', 'banana', 'apple'),
'veggie' => array('carrot', 'collard', 'pea'));
// 递归计数
var_dump(count($food, COUNT_RECURSIVE));
// 常规计数
var_dump(count($food));
?>
以上例程会输出：
int(8) int(2)
示例 #4 Countable 对象
<?php
class CountOfMethods implements Countable
{
private function someMethod()
{
}
public function count(): int
{
return count(get_class_methods($this));
}
}
$obj = new CountOfMethods();
var_dump(count($obj));
?>
以上例程会输出：
int(2)
参见
- is_array() - 检测变量是否是数组
- isset() - 检测变量是否已声明并且其值不为 null
- empty() - 检查一个变量是否为空
- strlen() - 获取字符串长度
- is_countable() - Verify that the contents of a variable is a countable value
- Array 数组
add a note
User Contributed Notes 19 notes
onlyranga at gmail dot com ¶
8 years ago
Christoph097 ¶
5 months ago
Empty values are counted:
<?php
$ar[] = 3;
$ar[] = null;
var_dump(count($ar)); //int(2)
?>
Anonymous ¶
2 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
lucasfsmartins at gmail dot com ¶
3 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.
danny at dannymendel dot com ¶
15 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 $count;
}
?>
alexandr at vladykin dot pp dot ru ¶
15 years ago
My function returns the number of elements in array for multidimensional arrays subject to depth of array. (Almost COUNT_RECURSIVE, but you can point on which depth you want to plunge).
<?php
function getArrCount ($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 $res;
}
?>
pied-pierre ¶
7 years ago
A function of one line to find the number of elements that are not arrays, recursively :
function count_elt($array, &$count=0){
foreach($array as $v) if(is_array($v)) count_elt($v,$count); else ++$count;
return $count;
}
php_count at cubmd dot com ¶
5 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;
}
?>
Gerd Christian Kunze ¶
8 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 ¶
5 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
JumpIfBelow ¶
7 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[$i]);
?>
jerome dot gds at gmail dot com ¶
2 years ago
to end the debate: count() is the same as empty()
test code below:
results on my computer:
count : double(0.81396999359131)
empty : double(0.81621310710907)
using isset($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);
buyatv at gmail dot com ¶
5 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 ¶
1 year ago
To get the count of the inner array you can do something like:
$inner_count = count($array[0]);
echo ($inner_count);
ThisIsNotImportant ¶
6 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 ¶
3 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 ¶
2 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($data, 1));
?>
XavDeb ¶
2 years ago
If you want to know the sub-array containing the MAX NUMBER of values in a 3 dimensions array, here is a try (maybe not the nicest way, but it works):
function how_big_is_the_biggest_sub ($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
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