数组 函数
在线手册：中文 英文
PHP手册

count

(PHP 4, PHP 5)

count — 计算数组中的单元数目或对象中的属性个数

说明

int count ( mixed $var [, int $mode ] )

返回 var 中的单元数目，通常是一个 array，任何其它类型都只有一个单元。

对于对象，如果安装了 SPL，可以通过实现 Countable 接口来调用 count()。该接口只有一个方法 count()，此方法返回 count() 函数的返回值。

如果 var 不是数组类型或者实现了 Countable 接口的对象，将返回 1，有一个例外，如果 var 是 NULL 则结果是 0。

Note: 可选的 mode 参数自 PHP 4.2.0 起可用。

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。mode 的默认值是 0。count() 识别不了无限递归。

Caution

count() 对没有初始化的变量返回 0，但对于空的数组也会返回 0。用 isset() 来测试变量是否已经初始化。

请参考手册中数组一节中关于怎样在 PHP 中实现和使用数组的详细解释。

Example #1 count() 例子

<?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 count() 的递归例子（PHP >= 4.2.0）

<?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
?>

参见 is_array()，isset() 和 strlen()。

数组 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: 计算数组中的单元数目或对象中的属性个数

用户评论:

nicolas dot grekas+php at gmail dot com (10-Sep-2011 07:29)

As of PHP 5.2.6, count() DOES detect infinite recursion.
It triggers a warning when its argument is a recursive array.

mike dot mackintosh at angrystatic dot com (08-Sep-2011 06:31)

If you try to do a sizeof or count with an object, it will always return 1 if the object is not null.

You need to type cast the object as an array for it to count correctly.

ex:

<?php
$obj->foo = 'fu';
$obj->bar = $fooBar();

echo count($obj); //returns 1

echo count( (array) $obj); // returns 2
?>

gothamxi (08-Mar-2011 06:48)

simple random value from array.

<?php
$topic=array(
    "UFOs",
    "Barack Obama",
    "China",
    "Christianity",
    "Communism",
    "World War II",
    "Global Warming",
    "Vegetarianism",
            );

echo ("What do you think about ".$topic[ rand( 1,count($topic) ) ]."? ");

?>

output-->
What do you think about Global Warming? , etc

pro at developergatsby dot com (15-Jan-2011 10:37)

Complexity of count function.

I just tested the complexity of count().
It looks O(1).

Here is the result.

<< counting array with 1 element>>
total time : 0.021ms
start -> end : 100 %

<< counting array with 100000 elements>>
total time : 0.015ms
start -> end : 100 %

Here is the testing code.
mini_bench_to is a function.
<?php

$arr = array();
$arr[] = "1";

$t['start'] = microtime(true);
$size = count($arr);
$t['end'] = microtime(true);
$str_result_bench = mini_bench_to($t);
echo $str_result_bench; // string return

$arr = array();
for($index = 0; $index < 100000; $index++) {
    $arr[] = $index;
}
$t['start'] = microtime(true);
$size = count($arr);
$t['end'] = microtime(true);
$str_result_bench=mini_bench_to($t);
echo $str_result_bench; // string return

?>

<?php
function mini_bench_to($arg_t, $arg_ra=false) {
    $tttime=round((end($arg_t)-$arg_t['start'])*1000,4);
    if ($arg_ra) $ar_aff['total_time']=$tttime;
    else $aff="total time : ".$tttime."ms\n";
    $prv_cle='start';
    $prv_val=$arg_t['start'];

    foreach ($arg_t as $cle=>$val)
    {
        if($cle!='start')   
        {
            $prcnt_t=round(((round(($val-$prv_val)*1000,4)/$tttime)*100),1);
            if ($arg_ra) $ar_aff[$prv_cle.' -> '.$cle]=$prcnt_t;
            $aff.=$prv_cle.' -> '.$cle.' : '.$prcnt_t." %\n";
            $prv_val=$val;
            $prv_cle=$cle;
        }
    }
    if ($arg_ra) return $ar_aff;
    return $aff;
}
?>

marc at example dot com (23-Sep-2010 08:10)

Just found use for this function...
Can count an array of items where a certain condition is met.
Feel free to improve it.

function countWhere($input = 1, $operator = '==', $where = 1)
{
    $input = is_array($input) ? $input : (array)$input;
    $operator = !in_array($operator, array('<','>','<=', '>=','==', '!=')) ? '==' : $operator;

    $i = 0;

    foreach($input as $current)
    {
        $match = null;
        eval('$match = (bool)("'.$current.'"'.$operator.'"'.$where.'");');

        $i = $match ? $i+1 : $i;
    }

    return $i;
}

USAGE:
echo countWhere(array('PZ','AB','CD','EF','GH'), '!=', 'GH');

OUTPUT:
4

marc at gutt dot it (07-Jun-2010 07:10)

There was a change in a PHP5 version. Now an empty string returns 1:
<?php
echo count(''); // returns 1
echo count(array()); // returns 0
?>

This wasn't in PHP4 and some older PHP5 versions.

D X (04-Mar-2010 02:42)

To know how much properties an object has, I do it like this:
count((array) $object)
... because count($object) gives me allways 1

ravenswd at gmail dot com (04-Aug-2009 08:37)

The code snippet posted by legobuff at hotmail dot com on 02-Feb-2000 contains an error. This is the code that was posted:

<?php
// To find the index of the last element in the array:
end($yourArray);
$index = key($yourArray);
?>

However, this will fail if the indices have been stored out of sequence. What you actually want is max(array_keys($yourArray)), as indicated below:

<?php
$yourArray = array(1=>'a', 7=>'b', 5=>'c');

print count($yourArray); // prints 3

end($yourArray);
print key($yourArray); // prints 5

print max(array_keys($yourArray)); // prints 7
?>

jezdec at email dot cz (20-Apr-2009 12:42)

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!";
?>

ceo at l-i-e dot com (17-Dec-2008 08:22)

count('') returns the very un-intuitive value of 1...

michael.debyl at gmail dot comz0r (16-Jul-2008 11:45)

There doesn't seem to be a succinct method already noted on this page for counting multidimensional array end nodes (Items in multidimensional arrays), so I thought this function might help somebody.

Nice and simple :)

<?php
function rcount ($array) {
  $count = 0;
  if (is_array($array)) {
    foreach($array as $id=>$sub) {
    if (!is_array($sub)) { $count++; }
     else { $count = ($count + rcount($sub)); }
    }
    return $count;
  }
  return FALSE;
}
?>

analpaper{gmail} (04-Jul-2008 03:37)

I found useful this little function that detects if a array is multidimensional or not.

<?php
function array_is2D($array) {
  return is_array($array) ? count($array)===count($array, COUNT_RECURSIVE) : -1;
}
?>

---
live2code

Anonymous (11-Jan-2008 09:20)

Here is an iterative soloution of danny's count_recursive function which might be more efficient due to the missing recursion

<?php
/**
 * counts elements of an multidimensional array
 *
 * @param array $array Input Array
 * @param int $limit dimensions that shall be considered (-1 means no limit )
 * @return int counted elements
 */
function multicount ($array, $limit = -1)
{
   $cnt = 0;
   $limit = $limit > 0 ? (int) $limit : -1;
   $arrs[] = $array;
   for ($i=0; isset($arrs[$i]) && is_array($arrs[$i]); ++$i)
   {
      foreach ($arrs[$i] as $value)
      {
         if (!is_array($value) ) ++$cnt;
         elseif( $limit==-1 || $limit>1 )
         {
            if( $limit>1 ) --$limit;
            $arrs[] = $value;
         }
      }
   }     
   return $cnt;
}
?>

atoi_monte at hotmail dot com (28-Jun-2007 10:10)

Please note: While SPL is compiled into PHP by default starting with PHP 5, the Countable interface is not available until 5.1

danny at dannymendel dot com (13-Jun-2007 09:14)

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, $limit)
{
    foreach ($array as $id => $_array)
    {
        if (is_array ($_array) && $limit > 0) $count += count_recursive ($_array, $limit - 1); else $count += 1;
    }
    return $count;
}
?>

yarolan at mail dot ru (26-Apr-2007 12:56)

NEVER USE IN CYCLES!

<?php
//size of $arr ~ 2000 elements

//wrong variant (Time exec ~ 19 sec)
for($i=0;$i<count($arr);$i++)
{
   //...
}

//right variant(Time exec ~ 0.2 sec)
$arr_size=count($arr);
for($i=0;$i<$arr_size;$i++)
{
   //...
}
?>

it was discovered experimentally.

Colin (03-Feb-2007 03:24)

<?php
// countValuesRecursive
// The goal of this function is to count non-false values of a multidimenional array
// This is useful in making a quick determination if a form sent any values
// If no values were sent I can simply return to the blank form rather than continuing to the validation of each input
// There are two limitations of the principle:
// 1. If you WANT to send FALSE, 0, '', or NULL as form values this function will not count those, thus not doing what's expected
// 2. This would create an endless loop on a form that has no required fields such as one where users can choose to recieve optional  email subscriptions but where choosing none is also valid
function countValuesRecursive($array, $count = 0) {
   
    // Cycle through the array
    foreach ($array as $value) {
       
        // Check if the value is an array
        if (is_array($value)) {
           
            // Cycle through deeper level
            $count = countValuesRecursive($value, $count);
            }
        else {
           
            // Check if the value is TRUE
            if ($value) {
                $count++;
                }
            }
        }
   
    // Return the count
    return $count;
    }
?>

alexandr at vladykin dot pp dot ru (08-Nov-2006 12:28)

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;
  }
?>

anil dot iitk at gmail dot com (26-Jan-2006 08:32)

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

// recursive count
echo "<br>".count($food, COUNT_RECURSIVE); // output 8

function average($a){
  return array_sum($a)/count($a) ;
}
$b = array(1,2,3,4,5,6,7,8,9);
echo "Average of array:".average($b);

?>

Scorch at netpix dot com (20-Dec-2005 01:59)

Be careful of recasting your variables, especially with database array returns:

<?php
$res = mysql_query("select * from blah") // a query that returns an empty set
$row = mysql_fetch_array($res); // get's 0 since there's no return
echo count($row); // echos 1 - since $row is not an array
echo $row[0]; // echos "", but casts $row as an array?
echo count($row); // echos 0 now
?>

Tom (01-Dec-2005 12:57)

You can find an average from an array using this and array_sum.
<?php
//array average( array input )
function average($input) {
return array_sum($input) / count($input);
}
?>

You can also do a method of form validation that involves putting all errors into an array and letting count() do the key part.
<?php
if(isset($_POST['submit'])) {
$errors = array();
if(empty($_POST['message'])) $errors[] = "Empty message field";
if(!preg_match('/[a-z0-9.]@[a-z0-9].[a-z]/i', $_POST['email']) {
$errors[] = "Bad email address";
  }
if(count($errors) == 0) {
//process form...
  }
}
?>

Fred D (18-Oct-2005 05:16)

The trim_text function was helpful, but it did not take account of the possibility of having nothing to trim which can sometimes happen if you are using this function in a loop through data. I've added a count function to deal with that possibility

<?php
function trim_text_elipse($text, $count){
//Create variable
$trimmed="";

//Remove double white space
$text = str_replace("  ", " ", $text);

//Turn the text into an array
$string = explode(" ", $text);

//Check to see how many words there are
$wordTotal = count($string);   
    //Check to see if there are more words than the $count variable
    if($wordTotal > $count){
        //Loop through adding words until the $count variable is reached
        for ( $wordCounter = 0; $wordCounter <= $count; $wordCounter++ ){
            $trimmed .= $string[$wordCounter];
                //Check to and add space or finish with elipse           
                if ( $wordCounter < $count ){ $trimmed .= " "; }
                else { $trimmed .= " &#8230;"; }
                }
    }else{
    //Set value returned to the existing value
    $trimmed =$text;
    }
//Trim off any white space   
$trimmed = trim($trimmed);
return $trimmed;
}

?>

david _at_ webgroup _dot_ org (13-Feb-2005 12:30)

While michael at htmlland dot net's code works, I believe it is better to use:
$extension=substr($file,strrpos($file,".")+1);

This doesn't incur the overhead of array handling.  I haven't tested it for time functions, but it should work just as well and SHOULD be faster.

freefaler at gmail dot com (20-Nov-2004 01:01)

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
?>

moazzam at ummah dot org (15-Oct-2004 12:59)

This is an obvious note, but I am writing it any way so other, who did may not have observed this, can take advantage of it too.

When running loops with count conditions, the code runs faster if you first assign the count() value to a variable and use that (instead of using count() directly in a loop condition.

To explain my point better, here is an example:

<?php

for ($i=0; $i<10000; $i++) {
    $arr[] = $i;
}

$time11 = microtime_float();
$bf = "";
for ($i=0; $i<count($arr); $i++) {
    $bf .= $arr[$i]."\n";
}
$time12 = microtime_float();
$time1 = $time12 - $time11;

print "First: ".$time1."\n";

$time21 = microtime_float();
$l = count($arr);
for ($i=0; $i<$l; $i++) {
    $bf .= $arr[$i]."\n";
}
$time22 = microtime_float();
$time2 = $time22 - $time21;

print "Second: ".$time2."\n";

?>

The output from the code above is (when run many times):

First: 0.13001585006714
Second: 0.099159002304077

First: 0.12128901481628
Second: 0.079941987991333

First: 0.18690299987793
Second: 0.13346600532532

As you can see, the second method (which doesnt use count() directly in the loop) is faster than the first method (which uses count() directly in the loop).

BTW:  I copied the microtime_float() function from one of the comments in the microtime() section. It just returns time with microseconds as float. Check comments in microtime() for more info.

michael at htmlland dot net (04-Jun-2004 06:30)

I have found on upload scripts or on file manipulation scripts that people can trick a classic file type filter:
example:

<?php
$filename="bob.jpg.wav";
$bits= explode(".",$filename);
$extention= $bits[1];
if($extention == "jpg"){ echo"Not correct"; exit; }
?>

This returns the filename extention as jpg not wav.

One way to change this is to use count() :
example:

<?php
$filename="bob.jpg.wav";
$bits= explode(".",$filename);
$extention= $bits[count($bits) - 1];
if($extention == "jpg"){ echo "Not correct"; exit; }
?>

This returns the filename extention as wav not jpg.

rolandfoxx at yahoo dot com (31-Mar-2004 12:13)

As an addition, any of the array manipulation functions can likewise get count to once again return 0:

<?php
$a = array();
print(count($a)); // prints 0
$a[0] = "foo";
array_shift($a);
print(count($a)); //prints 0
$a[0] = "bar";
array_splice($a, 0, 1);
print(count($a)); //prints 0
?>

admin at lft-muenchen dot de (12-Mar-2003 12:18)

Note:

<?php
print (strlen($a)); // will print 0
$a="";
print (strlen($a)); // will print 1
$a=null;
print (strlen($a)); // will print 1
$a=array();
print (strlen($a)); // will print 0
?>

you can only get an array back to size 0 by using the array() command, not by just setting it to "" or null.

simon at invalid dot com (20-Aug-2002 08:40)

Reminder for using count():

<?php
$ary = array(null, "a", "b", null);
echo count($ary);    // count: 4

$ary[10] = "c";
echo count($ary);    // count: 5

$ary[15] = null;
echo count($ary);    // count: 6
?>

=> NULL is seen as an element in count()

Count 2D array:

<?php
$a2Dary = array(array("a", "b") , array(), "v");

echo count($a2Dary);        // count: 3
echo count($a2Dary[0]);    //count 2
echo count($a2Dary[1]);    // count: 0
echo count($a2Dary[2]);    // count: 1
?>

Hope can help you

webmaster at NOSPAMtrafficg dot com (26-Apr-2002 11:48)

Counting a multi-dimentional array

test array

<?php
$settings[0][0]  = 128;
$settings[0][1]  = 256;
$settings[0][2]  = 384;
$settings[0][3]  = 512;
$settings[0][4]  = 1024;
$settings[0][5]  = 2048;

$settings[1][0]  = 1024;
$settings[1][1]  = 2048;
$settings[1][2]  = 3072;
$settings[1][3]  = 4096;

count($settings) // returns 2
count($settings[0]) // returns 6
count($settings[1]) // returns 4
?>

kanareykin at denison dot edu (26-Mar-2001 09:13)

Here's how to count non-empty elements
in an array of any dimension. Hope
it will be useful for somebody.

<?php
// recursively count all non-empty elements
// in array of any dimension or mixed - i.e.
// array('1' => 2, '2' => array('1' => 3, '2' => 4))
function count_all($arg)
{
    // skip if argument is empty
    if ($arg)    {
        // not an array, return 1 (base case)
        if(!is_array($arg))
            return 1;
        // else call recursively for all elements $arg
        foreach($arg as $key => $val)
            $count += count_all($val);
           
        return $count;       
    }
}
?>

martin at complinet dot com (30-Nov-2000 12:31)

The count function does not ignore null values in an array. To achieve this use this function.

<?php
function xcount($array) {
        while (list($key, $value) = each($array)) {
                if ($value) {
                        $count++;
                }
        }
return $count;
}
?>

jmcastagnetto at php dot net (04-Sep-2000 08:30)

If you want to disambiguate if a variable contains an array w/ only one element, just us is_array() or gettype()

legobuff at hotmail dot com (02-Feb-2000 06:43)

This is taken from sganer@expio.co.nz comments on the sizeof() function:
If some elements in your array are not set, then sizeof() and count() will not return the index of the last element, but will return the number of set elements. To find the index of the last element in the array:

end($yourArray);
$index = key($yourArray);

... Where $yourArray is the array you want to find the last index ($index) of.