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array_intersect_key

(PHP 5 >= 5.1.0, PHP 7)

array_intersect_key — キーを基準にして配列の共通項を計算する

説明

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

array_intersect_key() は、 array1 のエントリのうち、その他のすべての引数の中に共通して存在するキーと一致するキーの値からなる配列を返します。

パラメータ

array1: 値を調べるもととなる配列。
array2: 値を比較する対象となる配列。
...: さらにそれ以外の配列。

返り値

array1 のエントリのうち、すべての引数に存在するキーのものを含む連想配列を返します。

例

例1 array_intersect_key() の例


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

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

上の例の出力は以下となります。

array(2) {
  ["blue"]=>
  int(1)
  ["green"]=>
  int(3)
}

この例では、両方の配列に存在するキーが 'blue' と 'green' だけであり、それが返されていることがわかります。また、ふたつの配列の間で 'blue' と 'green' に対応する値が違うことにも注意しましょう。それでも一致していると判定されるのは、ただキーだけがチェックされているからです。返される値は array1 のものです。

二つの要素は、 (string) $elem1 === (string) $elem2 の場合のみ等しいとみなされます。言い換えると、文字列表現が同じ場合となります。

参考

array_diff() - 配列の差を計算する
array_udiff() - データの比較にコールバック関数を用い、配列の差を計算する
array_diff_assoc() - 追加された添字の確認を含めて配列の差を計算する
array_diff_uassoc() - ユーザーが指定したコールバック関数を利用し、追加された添字の確認を含めて配列の差を計算する
array_udiff_assoc() - データの比較にコールバック関数を用い、追加された添字の確認を含めて配列の差を計算する
array_udiff_uassoc() - データと添字の比較にコールバック関数を用い、追加された添字の確認を含めて配列の差を計算する
array_diff_key() - キーを基準にして配列の差を計算する
array_diff_ukey() - キーを基準にし、コールバック関数を用いて配列の差を計算する
array_intersect() - 配列の共通項を計算する
array_intersect_assoc() - 追加された添字の確認も含めて配列の共通項を確認する
array_intersect_uassoc() - 追加された添字の確認も含め、コールバック関数を用いて配列の共通項を確認する
array_intersect_ukey() - キーを基準にし、コールバック関数を用いて配列の共通項を計算する

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User Contributed Notes 13 notes

down

vladas dot dirzys at gmail dot com ¶

3 years ago


Simple key white-list filter:



<?php

$arr = array('a' => 123, 'b' => 213, 'c' => 321);

$allowed = array('b', 'c');



print_r(array_intersect_key($arr, array_flip($allowed)));

?>



Will return:

Array

(

    [b] => 213

    [c] => 321

)

down

pgl at yoyo dot org ¶

4 years ago


Note that the order of the keys in the returned array is the same as the order of the keys in the source array. eg:

<?php
$array = array(
    'two'   => 'a',
    'three' => 'b',
    'one'   => 'c',
    );

$keyswant = array(
    'one'       => '',
    'three'     => '',
    );

print_r(array_intersect_key($array, $keyswant));

?>

Shows:

Array
(
    [three] => b
    [one] => c
)

down

CBWhiz at gmail dot com ¶

8 years ago


I have found the following helpful:
<?PHP
function array_merge_default($default, $data) {
        $intersect = array_intersect_key($data, $default); //Get data for which a default exists
        $diff = array_diff_key($default, $data); //Get defaults which are not present in data
        return $diff + $intersect; //Arrays have different keys, return the union of the two
}
?>
It's use is like both of the functions it uses, but keeps defaults and _only_ defaults. It's designed for key arrays, and i'm not sure how it will work on numeric indexed arrays.

Example:
<?PHP
$default = array(
 "one" => 1,
 "two" => 2
);
$untrusted = array(
 "one" => 42,
 "three" => 3
);
var_dump(array_merge_default($default, $untrusted));

array(2) {
  ["two"]=>
  int(2)
  ["one"]=>
  int(42)
}

?>

down

Reed Silver ¶

11 months ago


If you want an array that has no key value pairs added from the second array:

$new = array_intersect_key($b, $a) + $a;

down

-1

github.com/xmarcos ¶

1 year ago


Here is a better way to merge settings using some defaults as a whitelist.

<?php

$defaults = [
    'id'            => 123456,
    'client_id'     => null,
    'client_secret' => null,
    'options'       => [
        'trusted' => false,
        'active'  => false
    ]
];

$options = [
    'client_id'       => 789,
    'client_secret'   => '5ebe2294ecd0e0f08eab7690d2a6ee69',
    'client_password' => '5f4dcc3b5aa765d61d8327deb882cf99', // ignored
    'client_name'     => 'IGNORED',                          // ignored
    'options'         => [
        'active' => true
    ]
];

var_dump(
    array_merge_recursive($defaults, 
        array_intersect_key(
            $options, $defaults
        )
    )
);

?>

Output:

array (size=4)
    'id'            => int 123456
    'client_id'     => int 789
    'client_secret' => string '5ebe2294ecd0e0f08eab7690d2a6ee69' (length=32)
    'options'       => 
        array (size=2)
            'trusted' => boolean false
            'active'  => boolean true

down

chrisbloom7 at gmail dot com ¶

6 years ago


Regarding php at keithtylerdotcom solution to emulate

<?php
$z = someFuncReturningAnArray()['some_key'];
?>

His recommended solution will still return an array. To get the value of a single key in an array returned by a function, simply add implode() to the recipe:

<?php
function someFuncReturningAnArray() {
  return array(
    'a' => 'b',
    'c' => 'd',
    'e' => 'f',
    'g' => 'h',
    'i' => 'j'
  );
}

//traditional way
$temp = someFuncReturningAnArray();
$b = $temp['a'];
echo print_r($b, 1) . "\n----------\n";

//keithtylerdotcom one-line method
$b = array_intersect_key(someFuncReturningAnArray(), array('a'=>''));
echo print_r($b, 1) . "\n----------\n";

//better one line method
$b = implode('', array_intersect_key(someFuncReturningAnArray(), array('a'=>'')));
echo print_r($b, 1) . "\n----------\n";
?>

down

pdemaziere at gmail dot com ¶

7 years ago


Just a simple script if you want to use one array, which contains only zeros and ones, as mask for another one (both arrays must have the same size of course). $outcome is an array that contains only those values from $source where $mask is equal to 1.



<?php

$outcome = array_values(array_intersect_key( array_values($source), array_filter(array_values($mask)) ));

?>



PS: the array_values() function is necessary to ensure that both arrays have the same numbering/keys, otherwise your masking does not behave as you expect.



Enjoy!

down

Anton Backer ¶

9 years ago


Jesse: no, array_intersect_key does not accomplish the same thing as what you posted:

array_flip (array_intersect (array_flip ($a), array_flip ($b)))

because when the array is flipped, values become keys. having duplicate values is not a problem, but having duplicate keys is. array_flip resolves it by keeping only one of the duplicates and discarding the rest. by the time you start intersecting, you've already lost information.

down

aidan at php dot net ¶

10 years ago


This functionality is now implemented in the PEAR package PHP_Compat.

More information about using this function without upgrading your version of PHP can be found on the below link:

http://pear.php.net/package/PHP_Compat

down

-1

Anonymous ¶

9 years ago


Here it is a more obvious way to implement the function:

if (!function_exists('array_intersect_key')) {
    function array_intersect_key()
    {
        $arrs = func_get_args();
        $result = array_shift($arrs);
        foreach ($arrs as $array) {
            foreach ($result as $key => $v) {
                if (!array_key_exists($key, $array)) {
                    unset($result[$key]);
                }
            }
        }
        return $result;
   }
}

down

-1

pixelf3hler at visualize-me dot de ¶

2 years ago


in case you came here looking for a function that returns an array containing the values of `all` arrays with intersecting keys:
<?php
   function array_merge_on_key($key, $array1, $array2) {
      $arrays = array_slice(func_get_args(), 1);
      $r = array();
      foreach($arrays as &$a) {
         if(array_key_exists($key, $a)) {
            $r[] = $a[$key];
            continue;
         }
      }
      return $r;
   }
   // example:
   $array1 = array("id" => 12, "name" => "Karl");
   $array2 = array("id" => 4, "name" => "Franz");
   $array3 = array("id" => 9, "name" => "Helmut");
   $array4 = array("id" => 10, "name" => "Kurt");

   $result = array_merge_on_key("id", $array1, $array2, $array3, $array4);

   echo implode(",", $result); // => 12,4,9,10
?>

down

-2

markus dot kappe at dix dot at ¶

6 years ago


<?php
    /**
     * calculates intersection of two arrays like array_intersect_key but recursive
     *
     * @param  array/mixed  master array
     * @param  array        array that has the keys which should be kept in the master array
     * @return array/mixed  cleand master array
     */
    function myIntersect($master, $mask) {
        if (!is_array($master)) { return $master; }
        foreach ($master as $k=>$v) {
            if (!isset($mask[$k])) { unset ($master[$k]); continue; } // remove value from $master if the key is not present in $mask
            if (is_array($mask[$k])) { $master[$k] = $this->myIntersect($master[$k], $mask[$k]); } // recurse when mask is an array
            // else simply keep value
        }
        return $master;
    }
?>

down

-2

Rod Byrnes ¶

8 years ago


Here is a faster version than those shown below, with optimisation for the case when only two arrays are passed. In my tests with a 10000 item first array and a 5000 item second array (run 20 times) this function ran in 1.89 seconds compared with 2.66 for the version posted by dak. For a three array case, same as above but with the third array containing 3333 values, the timing is 3.25 for this version compared with 3.7 for dak's version.

<?php
if (!function_exists('array_intersect_key'))
{
  function array_intersect_key($isec, $keys)
  {
    $argc = func_num_args();
    if ($argc > 2)
    {
      for ($i = 1; !empty($isec) && $i < $argc; $i++)
      {
        $arr = func_get_arg($i);
        foreach (array_keys($isec) as $key)
        {
          if (!isset($arr[$key]))
          {
            unset($isec[$key]);
          }
        }
      }
      return $isec;
    }
    else
    {
      $res = array();
      foreach (array_keys($isec) as $key)
      {
        if (isset($keys[$key]))
        {
          $res[$key] = $isec[$key];
        }
      }
      return $res;
    }
  }
}
?>

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