[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 — Conta gli elementi in una variabile, o le proprietà in un oggetto
Descrizione
Restituisce il numero di elementi in var,
la quale è di norma un array, dal momento che qualsiasi altro oggetto
avrà un elemento.
Per gli oggetti, se
SPL è installato, è possibile agganciarsi a
count() implementando l'interfaccia
Countable. L'interfaccia ha esattamente un metodo,
count(), che ritorna il valore restituito dalla
funzione count().
Se var non è un array o un oggetto con
l'interfaccia Countable implementata,
verrà restituito 1
C'è una eccezione, se var è null,
verrà restituito 0.
Nota: Il parametro opzionale
modeè disponibile da PHP 4.2.0.
Se il parametro opzionale mode è impostato a
COUNT_RECURSIVE (o 1), count()
conterà ricorsivamente l'array. Questo è utile in particolare per
contare tutti gli elementi di un array multidimensionale. Il valore di
default per mode è 0.
count() non identifica le ricorsioni infinite.
Attenzione
count() può restituire 0 per una variabile che non è impostata, ma può anche restituire 0 per una variabile che è stata inizializzata con un array vuoto. Usare isset() per verificare se una variabile è impostata.
Vedere la sezione Array nel manuale per una spiegazione dettagliata di come gli array siano implementati ed usati in PHP.
Example #1 esempio di count()
<?php
$a[0] = 1;
$a[1] = 3;
$a[2] = 5;
$risultato = count($a);
//$risultato == 3
$b[0] = 7;
$b[5] = 9;
$b[10] = 11;
$risultato = count($b);
// $risultato == 3;
$result = count(null);
// $result == 0
$result = count(false);
// $result == 1
?>
Example #2 esempio di count() ricorsiva (PHP >= 4.2.0)
<?php
$cibo = array('frutta' => array('arancia', 'banana', 'mela'),
'verdura' => array('carota', 'zucchina', 'piselli'));
// conteggio ricorsivo
echo count($cibp,COUNT_RECURSIVE); // output 8
// conteggio normale
echo count($cibo); // output 2
?>Vedere anche is_array(), isset() e strlen().
add a note
User Contributed Notes 18 notes
onlyranga at gmail dot com ¶
10 years ago
Anonymous ¶
5 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 ¶
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.
Christoph097 ¶
2 years ago
Empty values are counted:
<?php
$ar[] = 3;
$ar[] = null;
var_dump(count($ar)); //int(2)
?>
danny at dannymendel dot com ¶
17 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;
}
?>
olja dot fb at gmail dot com ¶
1 year ago
In example #3, given as:
<?php
$food = array('fruits' => array('orange', 'banana', 'apple'),
'veggie' => array('carrot', 'collard', 'pea'));
// recursive count
var_dump(count($food, COUNT_RECURSIVE));
?>
with the output given as int(8), it may have some readers mistaken, as I was at first: one might take it as keys being counted as well as the inner array entries:
<?php
// NO:
'fruits', 'orange', 'banana', 'apple',
'veggie', 'carrot', 'collard', 'pea'
?>
But actually keys are not counted in count function, and why it is still 8 - because inner arrays are counted as entries as well as their inner elements:
<?php
// YES:
array('orange', 'banana', 'apple'), 'orange', 'banana', 'apple',
array('carrot', 'collard', 'pea'), 'carrot', 'collard', 'pea'
?>
alexandr at vladykin dot pp dot ru ¶
18 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 $res;
}
?>
pied-pierre ¶
9 years ago
A function of one line to find the number of elements that are not arrays, recursively :
function count_elt($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 ¶
8 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 ¶
11 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
JumpIfBelow ¶
9 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]);
?>
vojtaripa at gmail dot com ¶
4 years ago
To get the count of the inner array you can do something like:
$inner_count = count($array[0]);
echo ($inner_count);
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
ThisIsNotImportant ¶
9 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))
?>
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
