array_diff_key

(PHP 5 >= 5.1.0, PHP 7)

array_diff_key — Computes the difference of arrays using keys for comparison

설명

array array_diff_key ( array $array1 , array $array2 [, array $... ] )

Compares the keys from array1 against the keys from array2 and returns the difference. This function is like array_diff() except the comparison is done on the keys instead of the values.

인수

array1: The array to compare from
array2: An array to compare against
...: More arrays to compare against

반환값

Returns an array containing all the entries from array1 whose keys are not present in any of the other arrays.

예제

Example #1 array_diff_key() example

The two keys from the key => value pairs are considered equal only if (string) $key1 === (string) $key2 . In other words a strict type check is executed so the string representation must be the same.


<?php
$array1 = array('blue'  => 1, 'red'  => 2, 'green'  => 3, 'purple' => 4);
$array2 = array('green' => 5, 'blue' => 6, 'yellow' => 7, 'cyan'   => 8);

var_dump(array_diff_key($array1, $array2));
?>

위 예제의 출력:

array(2) {
  ["red"]=>
  int(2)
  ["purple"]=>
  int(4)
}

주의

Note:
This function only checks one dimension of a n-dimensional array. Of course you can check deeper dimensions by using array_diff_key($array1[0], $array2[0]);.

참고

array_diff() - 배열 차이를 계산
array_udiff() - 데이터 비교 콜백함수를 사용하여 배열간의 차이를 계산
array_diff_assoc() - 추가적인 인덱스 확인과 함께 배열 차이를 계산
array_diff_uassoc() - Computes the difference of arrays with additional index check which is performed by a user supplied callback function
array_udiff_assoc() - Computes the difference of arrays with additional index check, compares data by a callback function
array_udiff_uassoc() - Computes the difference of arrays with additional index check, compares data and indexes by a callback function
array_diff_ukey() - Computes the difference of arrays using a callback function on the keys for comparison
array_intersect() - 배열의 교집합을 계산
array_intersect_assoc() - 인덱스 검사과 함께 배열의 교집합을 계산
array_intersect_uassoc() - Computes the intersection of arrays with additional index check, compares indexes by a callback function
array_intersect_key() - Computes the intersection of arrays using keys for comparison
array_intersect_ukey() - Computes the intersection of arrays using a callback function on the keys for comparison

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User Contributed Notes 11 notes

down

Ashton ¶

16 years ago


To return the unique elements (those with a key that exists only once in either array but not in both) try:
function array_unique_diff ($array1, $array2)
{
  array_merge(array_diff_key($array1, $array2), array_diff_key($array2, $array1));
}

Example:
$array1 = array('blue'  => 1, 'red'  => 2, 'green'  => 3, 'purple' => 4);
$array2 = array('green' => 5, 'blue' => 6, 'yellow' => 7, 'cyan'   => 8);

  array_diff_key($array1, $array2)

returns

  array ( 'red' => 2, 'purple' => 4 ) 

  array_diff_key($array2, $array1)

returns

  array ( 'yellow' => 7, 'cyan' => 8, )

  array_unique_diff($array1, $array2);
  
returns

  array ( 'red' => 2, 'purple' => 4, 'yellow' => 7, 'cyan' => 8, )

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gk at anuary dot com ¶

11 years ago


Improved recursive version.

<?php
/**
 * @author Gajus Kuizinas <gk@anuary.com>
 * @version 1.0.0 (2013 03 19)
 */
function array_diff_key_recursive (array $arr1, array $arr2) {
    $diff = array_diff_key($arr1, $arr2);
    $intersect = array_intersect_key($arr1, $arr2);
    
    foreach ($intersect as $k => $v) {
        if (is_array($arr1[$k]) && is_array($arr2[$k])) {
            $d = array_diff_key_recursive($arr1[$k], $arr2[$k]);
            
            if ($d) {
                $diff[$k] = $d;
            }
        }
    }
    
    return $diff;
}
?>

An up to date version is maintained at https://github.com/gajus/flow/blob/master/flow.inc.php#L337.

down

sjungwirth at matrix-consultants dot com ¶

16 years ago


I needed something a little different where maybe even the keys in multidimensional arrays don't match up. Setting $assoc to false will cause only to check for missing keys, otherwise it compares values as well. This was also based on '2ge at 2ge dot us' function

<?php

function n_array_diff_assoc ($a1, $a2, $assoc=true) {
    $r = array();
    if(is_array(current($a1))):
        foreach($a1 as $k => $v):
            if(isset($a2[$k])):
                $diff = n_array_diff($a1[$k], $a2[$k], $assoc);
                if (!empty($diff)):
                    $r[$k] = $diff;
                endif;
            else:
                $r[$k] = $v;
            endif;
        endforeach;
    else:
        $r = $assoc ? array_diff_assoc($a1, $a2) : array_diff_key($a1, $a2);
    endif;
    return $r;
}
?>

down

maxence at pontapreta dot net ¶

19 years ago


Seems to be a great function, especially for n-dimensions arrays. The only problem is that I cannot find it in php 5.0.3 and 5.0.4. Does it really exist ?! :(

[20:27:05][maxence@conurb] ~/test2/php-5.0.4$ grep PHP_FUNCTION * -r | grep -i array_diff_key 
[20:27:09][maxence@conurb] ~/test2/php-5.0.4$

down

AiFiLTr0 [at host] invyl [dot] ath.cx ¶

17 years ago


The recursive function suggested by '2ge at 2ge dot us' will provide you with empty arrays if there's no diff. 
This variant of the function cleans up empty arrays and fixes a bug in the first suggested version. It works 100%
.
<?php
function array_diff_key_recursive ($a1, $a2) {
        foreach($a1 as $k => $v) {
            //$r[$k] = is_array($v) ? $this->array_diff_key_recursive($a1[$k], $a2[$k]) : array_diff_key($a1, $a2);
        if (is_array($v))
            {
            $r[$k]=$this->array_diff_key_recursive($a1[$k], $a2[$k]);
            }else
            {
            $r=array_diff_key($a1, $a2);
            }

        if (is_array($r[$k]) && count($r[$k])==0)
            {
            unset($r[$k]);
            }
        }
        return $r;
    }
?>

down

coder at gs dot com ¶

16 years ago


The PHP4 version below works only unidirectionally. If you switch the arrays around i.e. (ar2, ar1) you get different results than (ar1, ar2).

down

ampf at egp dot up dot pt ¶

19 years ago


Well, you could implement in the code something more powerfull: 

http://www.php.net/manual/en/function.array-diff.php#31364

down

-2

division-par-zero at zilon dot net ¶

16 years ago


you can use this function for return the difference of two array !



<?php

function array_unique_diff_key ($array1, $array2)

{

  if (is_array($array1) && is_array($array2))

    return array_diff_key($array1, $array2) + array_diff_key($array2, $array1);

  else if (is_array($array1)) return $array1;

  else if (is_array($array2)) return $array2;

  else return array();

}

?>

down

-3

vlad_mustafin at ukr dot net ¶

18 years ago


One more alternative variant :)
<?
if (!function_exists('array_diff_key')) {
    function array_diff_key() {
        $argCount   = func_num_args();
        $diff_arg_prefix = 'diffArg';
        $diff_arg_names = array();
        for ($i=0; $i < $argCount; $i++) {
            $diff_arg_names[$i] = 'diffArg'.$i;
            $$diff_arg_names[$i] = array_keys((array)func_get_arg($i));
        }
        $diffArrString = '';
        if (!empty($diff_arg_names)) $diffArrString =  '$'.implode(', $', $diff_arg_names);
        eval("\$result = array_diff(".$diffArrString.");");
        return $result;
    }
}
?>

down

-2

rhallsey at yahoo dot com ¶

10 years ago


Here's a simple function that returns true if all keys in the first array are found in the second array, and false if they aren't.

function same_keys ($a1, $a2) {
    $same = false;
    if (!array_diff_key($a1, $a2)) {
        $same = true;
        foreach ($a1 as $k => $v) {
            if (is_array($v) && !same_keys($v, $a2[$k])) {
                $same = false;
                break;
            }
        }
    }
    return $same;
}

To check if two arrays have the same structure, ignoring values, execute the function twice, the second time with the arguments reversed.

down

-5

2ge at 2ge dot us ¶

18 years ago


Hello, if you need diff key of n-dimensional arrays here is nice solution:
<?php
function n_array_diff ($a1, $a2) {
        foreach($a1 as $k => $v) {
            $r[$k] = is_array($v) ? n_array_diff($a1[$k], $a2[$k]) : array_diff_key($a1, $a2);
        }
        return $r;
}
?>
it will print everything, what is missing in $a2.

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