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    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。

    更新日志

    版本 说明
    8.0.0 现在可以仅使用一个参数调用此函数。以前，至少需要两个参数。

    示例

    示例 #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));
    ?>

    以上示例会输出：

    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

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    User Contributed Notes 11 notes

    up
    265
    vladas dot dirzys at gmail dot com
    12 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
    )
    up
    10
    Anonymous
    3 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.

    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
    )
    up
    22
    github.com/xmarcos
    10 years ago
    [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
    up
    5
    Reed Silver
    9 years ago
    If you want an array that has no key value pairs added from the second array:

    $new = array_intersect_key($b, $a) + $a;
    up
    11
    pgl at yoyo dot org
    13 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
    )
    up
    6
    CBWhiz at gmail dot com
    16 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)
    }

    ?>
    up
    3
    Anton Backer
    18 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.
    up
    1
    chrisbloom7 at gmail dot com
    15 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";
    ?>
    up
    0
    markus dot kappe at dix dot at
    15 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     $master;
        }
    ?>
    up
    -2
    pixelf3hler at visualize-me dot de
    11 years ago
    in case you came here looking for a function that returns an array containing the values of `all` arrays with intersecting keys:
    <?php
           function array_merge_on_key($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
    ?>
    up
    -4
    pdemaziere at gmail dot com
    15 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!
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