count

(PHP 4, PHP 5)

countZählt alle Elemente eines Arrays oder etwas in einem Objekt

Beschreibung

int count ( mixed $array_or_countable [, int $mode = COUNT_NORMAL ] )

Zählt alle Elemente eines Arrays oder etwas in einem Objekt.

Wenn Sie die SPL installiert haben, können Sie in Objekten eine count()-Funktion nutzen, indem Sie das Interface Countable implementieren. Das Interface hat exakt eine Methode, nämlich Countable::count(), die den Rückgabewert der Funktion count() zurückliefert.

In der Sektion Arrays finden Sie eine detaillierte Erklärung, wie Arrays in PHP implementiert sind und wie sie benutzt werden.

Parameter-Liste

array_or_countable

Ein Array oder Countable Objekt.

mode

Wenn der optionale Parameter mode auf COUNT_RECURSIVE (oder 1) gesetzt ist, wird count() rekursiv durch das Array zählen. Dies kann besonders nützlich sein, um alle Elemente eines mehrdimensionalen Arrays zu zählen.

Achtung

count() kann Rekursion erkennen, um eine Endlosschleife zu vermeiden, wird aber jedes Mal, wenn es das tut, ein E_WARNING erzeugen (im Fall, dass das Array sich selbst mehr als einmal enthält), und gibt dann eine höhere Anzahl zurück als möglicherweise erwartet.

Rückgabewerte

Liefert die Anzahl von Elementen in array_or_countable.

Ist der Parameter kein Array oder Objekt mit implementiertem Countable Interface, wird 1 zurückgegeben. Es besteht eine Ausnahme, wenn var NULL ist, wird 0 zurückgegeben.

Achtung

count() gibt 0 zurück, wenn die Variable nicht gesetzt ist, aber sie gibt ebenfalls 0 zurück, wenn die Variable als leeres Array initialisiert wurde. Verwenden Sie isset() um zu testen, ob eine Variable gesetzt ist.

Beispiele

Beispiel #1 count()-Beispiel

<?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
?>

Beispiel #2 Rekursives count()-Beispiel

<?php
$food 
= array('Obst' => array('Orange''Banane''Apfel'),
              
'Gemüse' => array('Karotte''Kohl''Erbse'));

// rekursiv zählen
echo count($foodCOUNT_RECURSIVE); // gibt 8 aus

// normales zählen
echo count($food); // gibt 2 aus

?>

Siehe auch

  • is_array() - Prüft, ob die Variable ein Array ist
  • isset() - Prüft, ob eine Variable existiert und ob sie nicht NULL ist
  • strlen() - Ermitteln der String-Länge

add a note add a note

User Contributed Notes 17 notes

up
27
onlyranga at gmail dot com
1 year ago
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
}
up
37
alexandr at vladykin dot pp dot ru
8 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;
  }
?>
up
25
danny at dannymendel dot com
7 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;
}
?>
up
4
Gerd Christian Kunze
1 year 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? ;-)
up
0
jingsoft at 126 dot com
4 months ago
There is an array:
$array = array ( 1, array( 1, 2, 3));
use count($array) will return 5, is a bug?
up
3
atoi_monte at hotmail dot com
7 years ago
Please note: While SPL is compiled into PHP by default starting with PHP 5, the Countable interface is not available until 5.1
up
-1
JumpIfBelow
19 days 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]);
?>
up
-5
jezdec at email dot cz
6 years ago
Hi there,
there is a simple script with example for counting rows and columns of a two-dimensional array.

<?php
$data
= array(
   
"apples" =>
        array(
"red", "yellow", "pineapples"),
   
"bananas" =>
        array(
"small", "medium", "big"),
   
"vegs" =>
        array(
"potatoes", "carrots", "onions")
);

$rows = count($data,0);
$cols = (count($data,1)/count($data,0))-1;
print
"There are {$rows} rows and {$cols} columns in the table!";
?>
up
-5
semmelbroesel at gmail dot com
1 year ago
I've read this somewhere else before, but experienced it first hand now, so I thought I'd post it here.

While in regular use, count() is pretty fast, this changes rapidly when used in a for loop. Example:

for ($x = 0; $x < count($array); $x++)
{
  // some code here
}

If your array contains a lot of data, this code gets slowed down significantly. Better way to write this:

$arrayCount = count($array);
for ($x = 0; $x < $arrayCount; $x++)
{
  // some code here
}

I didn't think it would make such a difference, but it did in my case - changed 15 seconds load time into 1 second!
up
-1
array at from dot pl
3 months ago
onlyranga at gmail dot com note about keeping count() in variable is not really correct, For some time now using variable and calling `count()` on each loop iteration costs you basically the same.

Proof: If you look into PHP sources then you see that for some time now it returns internal counter value instead of counting on each call. Here is `count` implementation: [1] where for array it calls `php_count_recursive` [2] which is then calls zend_hash_num_elements and returns `nNumOfElements` internal variable. It is not counting anything.

You may want to read this blog post about PHP internals too: https://nikic.github.io/2012/03/28/Understanding-PHPs-internal-array-implementation.html

[1] https://github.com/php/php-src/blob/PHP-5.5/ext/standard/array.c#L306
[2] https://github.com/php/php-src/blob/e10e151e9b92313a7085272c85bebf6c82017fce/ext/standard/array.c#L264
up
-7
MaxTheDragon at home dot nl
1 year ago
If you wish to test if an array contains any elements (or is empty), you might tempted to use count to do something like this:

<?php
if (count($my_array) > 0) {
// array is not empty...
}

// or this ...

if (count($my_array) === 0) {
// array is empty...
}
?>

Using the count function here is totally unnecessary and slower.

Instead, you should rely on the fact that empty arrays evaluate to false when cast to a boolean:

<?php
$hasElements
= (boolean) $my_array;

// or ...

$isEmpty = !$my_array;

// or in a conditional statement...

if ($my_array) {
// array is not empty...
}
?>

Only use count if you need to know if an array contains a specific number of elements n (where n > 0).
up
-24
freefaler at gmail dot com
10 years ago
If you want to count only elements in the second level of 2D arrays.A close to mind note, useful for multidimentional arrays:

<?php
$food
= array('fruits' => array('orange', 'banana', 'apple'),
            
'veggie' => array('carrot', 'collard','pea'));

// recursive count
echo count($food,COUNT_RECURSIVE);  // output 8

// normal count
echo count($food);                  // output 2

// all the fruits and veggies
echo (count($food,COUNT_RECURSIVE)-count($food,0)); //output 6
?>
up
-11
lopezvit at gmail dot com
1 year ago
I think that maybe that is faster (I don't know why, because, at least in C, for loops are faster than while ones due to compile optimization) but what is sure is that, in case the list is empty, you are going to iterate over the loop at least one. And I'm sure that is not what you want to do. The correct way in this occassion is to use a normal while, not a do, while.
up
-28
nicolas dot grekas+php at gmail dot com
3 years ago
As of PHP 5.2.6, count() DOES detect infinite recursion.
It triggers a warning when its argument is a recursive array.
up
-10
norbyte
1 year ago
If you want to check whether large arrays contain a specific (less) number of array elements, don't use count(). This is very slow because each element has to get iterated.

This is much faster:

function isArrayCount(array $array, $count) {
    $count = (int) $count;
    $result = reset($array);
    if ($count === 0) {
        // for empty arrays reset returns FALSE
        // we have to switch the boolean result
        $result = !$result;
    }
    for($i = 1; $i < $count; $i++) {
        if (next($array) === FALSE) {
            $result = FALSE;
            break;
        }
    }
    return $result;
}
up
-8
softontherocks at gmail dot com
6 months ago
I posted in my blog a small article talking about this function. If you want to visit it look at this url:

http://softontherocks.blogspot.com/2014/10/contar-los-elementos-de-un-array-en-php.html
up
-43
me at me dot com
1 year ago
To the poster above, the fastest way is to use 'do/while'. Try this way, you will find it faster than 'for'.
$arrayCount = count($array);
do{
    // some code here
    --$arrayCount;
}
while($arrayCount > 0);
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