array_intersect_key

(PHP 5 >= 5.1.0)

array_intersect_keyComputes the intersection of arrays using keys for comparison

Description

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

array_intersect_key() returns an array containing all the entries of array1 which have keys that are present in all the arguments.

Parameters

array1

The array with master keys to check.

array2

An array to compare keys against.

...

A variable list of arrays to compare.

Return Values

Returns an associative array containing all the entries of array1 which have keys that are present in all arguments.

Examples

Example #1 array_intersect_key() example

<?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));
?>

The above example will output:

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

In our example you see that only the keys 'blue' and 'green' are present in both arrays and thus returned. Also notice that the values for the keys 'blue' and 'green' differ between the two arrays. A match still occurs because only the keys are checked. The values returned are those of array1.

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.

See Also

  • array_diff() - Computes the difference of arrays
  • array_udiff() - Computes the difference of arrays by using a callback function for data comparison
  • array_diff_assoc() - Computes the difference of arrays with additional index check
  • 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_key() - Computes the difference of arrays using keys for comparison
  • array_diff_ukey() - Computes the difference of arrays using a callback function on the keys for comparison
  • array_intersect() - Computes the intersection of arrays
  • array_intersect_assoc() - Computes the intersection of arrays with additional index check
  • array_intersect_uassoc() - Computes the intersection of arrays with additional index check, compares indexes by a callback function
  • array_intersect_ukey() - Computes the intersection of arrays using a callback function on the keys for comparison

Коментарии

Автор:
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.
2006-03-31 02:49:50
http://php5.kiev.ua/manual/ru/function.array-intersect-key.html
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)
}

?>
2008-01-04 16:04:30
http://php5.kiev.ua/manual/ru/function.array-intersect-key.html
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
$outcome 
array_values(array_intersect_keyarray_values($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!
2009-02-23 09:52:26
http://php5.kiev.ua/manual/ru/function.array-intersect-key.html
<?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;
    }
?>
2009-09-24 07:43:56
http://php5.kiev.ua/manual/ru/function.array-intersect-key.html
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 $temp['a'];
echo 
print_r($b1) . "\n----------\n";

//keithtylerdotcom one-line method
$b array_intersect_key(someFuncReturningAnArray(), array('a'=>''));
echo 
print_r($b1) . "\n----------\n";

//better one line method
$b implode(''array_intersect_key(someFuncReturningAnArray(), array('a'=>'')));
echo 
print_r($b1) . "\n----------\n";
?>
2009-11-11 12:23:06
http://php5.kiev.ua/manual/ru/function.array-intersect-key.html
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
)
2011-07-18 11:01:11
http://php5.kiev.ua/manual/ru/function.array-intersect-key.html
Simple key white-list filter:

<?php
$arr 
= array('a' => 123'b' => 213'c' => 321);
$allowed = array('b''c');

print_r(array_intersect_key($arrarray_flip($allowed)));
?>

Will return:
Array
(
    [b] => 213
    [c] => 321
)
2012-08-13 11:03:59
http://php5.kiev.ua/manual/ru/function.array-intersect-key.html
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
?>
2013-09-28 11:08:48
http://php5.kiev.ua/manual/ru/function.array-intersect-key.html
Автор:
[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
2014-05-12 08:47:46
http://php5.kiev.ua/manual/ru/function.array-intersect-key.html
Автор:
If you want an array that has no key value pairs added from the second array:

$new = array_intersect_key($b, $a) + $a;
2015-03-03 01:38:44
http://php5.kiev.ua/manual/ru/function.array-intersect-key.html
Автор:
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
)
2021-08-19 14:38:52
http://php5.kiev.ua/manual/ru/function.array-intersect-key.html

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