array_intersect_key

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

array_intersect_key — 使用键名比较计算数组的交集

说明

array_intersect_key ( array $array , array ...$arrays ) : array

array_intersect_key() 返回一个数组，该数组包含了所有出现在 array 和其它参数数组中同时存在的键名的值。

参数

array

要检查的数组，作为主值。

arrays

要被对比的数组。

返回值

返回一个关联数组，该数组包含了所有出现在 array 和其它参数数组中同时存在的键名的值。

范例

Example #1 array_intersect_key() 例子

<?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));
?>

以上例程会输出：

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

上例中可以看到，只有 'blue' 和 'green' 两个键名同时出现在两个数组中，因此被返回。另外注意 'blue' 和 'green' 的值在两个数组中是不同的。但因为只检查键名，因此还是匹配。返回的只是 array 中的值。

在 key => value 对中的两个键名仅在 (string) $key1 === (string) $key2 时才被认为相等。换句话说，执行了严格的类型检查，因此字符串的表达形式必须相同。

参见

User Contributed Notes

Anonymous 19-Aug-2021 11:38
Note that the order of the keys in the returned array is the same as the order of the keys in the source array.

To sort by the second array, then you may do so through array_replace.

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

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

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

?>

Shows:

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

Rather than:

Array
(
    [three] => b
    [one] => c
)
Reed Silver 02-Mar-2015 11:38
If you want an array that has no key value pairs added from the second array:

$new = array_intersect_key($b, $a) + $a;
github.com/xmarcos 12-May-2014 05:47
[Editor's note: changed array_merge_recursive() to array_replace_recursive() to fix the script]

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_replace_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
pixelf3hler at visualize-me dot de 28-Sep-2013 08:08
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
?>
vladas dot dirzys at gmail dot com 13-Aug-2012 08:03
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
)
pgl at yoyo dot org 18-Jul-2011 08:01
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
)
chrisbloom7 at gmail dot com 11-Nov-2009 10:23
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";
?>
markus dot kappe at dix dot at 24-Sep-2009 04:43
<?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;
    }
?>
pdemaziere at gmail dot com 23-Feb-2009 07:52
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!
CBWhiz at gmail dot com 04-Jan-2008 02:04
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)
}

?>
Anton Backer 30-Mar-2006 11:49
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.
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