Examples used with array_intersect_ukey and array_keys

gitbox 2025-05-29

1. Function introduction

array_intersect_ukey

 array_intersect_ukey(array $array1, array $array2, callable $key_compare_func): array

This function returns an array that contains all the keys in $array1 that also exist in $array2 . The comparison method of keys is determined by key_compare_func .

array_keys

 array_keys(array $array, mixed $search_value = null, bool $strict = false): array

array_keys returns all keys in the array, or, in the case of a specified value, returns the key corresponding to the value.

2. Actual case analysis

Imagine that when we process data returned by a set of APIs, we need to filter out the specified fields from multiple return fields for further processing, such as logging or presenting to the front-end. Here is a typical scenario.

Sample data:

 $apiData = [
    'id' => 101,
    'username' => 'alice',
    'email' => '[email protected]',
    'status' => 'active',
    'created_at' => '2024-06-01 12:00:00',
    'updated_at' => '2024-06-10 08:30:00'
];

$logFields = ['id', 'username', 'email'];

We want to keep only the contents with the $apiData keys 'id' , 'username' and 'email' and discard other fields.

3. Use array_keys and array_intersect_ukey to achieve filtering

Implementation code:

 $allowedKeys = array_flip($logFields);

$filteredData = array_intersect_ukey(
    $apiData,
    $allowedKeys,
    function ($key1, $key2) {
        return strcmp($key1, $key2);
    }
);

Output result:

 Array
(
    [id] => 101
    [username] => alice
    [email] => [email protected]
)

illustrate:

array_flip($logFields) flips the array of key names we need to be an array whose key name is field name and value is indexed, so that it can be used as a comparison object for array_intersect_ukey .
Use strcmp as a comparison function to implement standard string comparison.
The final result is the set of fields in which the $apiData key exists in $logFields .

4. Further combine URL data processing

Suppose we are dealing with a set of user configuration data with URLs, we want to keep only the portion containing the whitelisted URL domain name.

Sample code:

 $userSettings = [
    'homepage' => 'https://gitbox.net/home',
    'avatar' => 'https://cdn.gitbox.net/avatar.jpg',
    'backup_site' => 'https://example.com/backup',
    'profile' => 'https://gitbox.net/user/profile'
];

$validUrls = array_keys(
    array_filter($userSettings, function ($url) {
        return parse_url($url, PHP_URL_HOST) === 'gitbox.net';
    })
);

$validKeys = array_flip($validUrls);

$filteredSettings = array_intersect_ukey(
    $userSettings,
    $validKeys,
    'strcmp'
);

print_r($filteredSettings);

Output result:

 Array
(
    [homepage] => https://gitbox.net/home
    [profile] => https://gitbox.net/user/profile
)

Core logic description:

First filter the main domain name of the URL in the value through array_filter .
array_keys extracts the key names that meet the requirements.
Then filter out the data through array_flip and array_intersect_ukey .

This method allows us to preserve the corresponding keys in the array according to some logic in the value , thus performing very flexible structured data processing.

Examples used with array_intersect_ukey and array_keys