array_intersect_ukey(): intersection between two arrays considering keys for checks through callback function

$new_array = array_intersect_ukey ($array1, $array2,....,my_function());

Example with two arrays

function my_function($a, $b)
{
    if ($a === $b) {
        return 0;
    }
    return ($a > $b)? 1:-1;
}

$first=array('One' =>'First','Two'=>'Second','Three'=>'Third','Fourth');
$second=array('1st'=> 'First','Two'=>'2nd','Three'=>'3rd','Fourth');

$result=array_intersect_ukey($first,$second,"my_function");
while (list ($key, $val) = each ($result)) {
echo "$key -> $val <br>";
}

Two -> Second 
Three -> Third 
0 -> Fourth 

Example 2: Using array_intersect_ukey() for Case-Insensitive Key Comparison

This example demonstrates how to use array_intersect_ukey() for case-insensitive key comparison, which is useful in scenarios where key case consistency isn't guaranteed.

function key_compare_func($key1, $key2) {
    return strcasecmp($key1, $key2);
}

$array1 = array('a' => 100, 'b' => 200, 'C' => 300);
$array2 = array('A' => 100, 'b' => 200, 'c' => 300);

$result = array_intersect_ukey($array1, $array2, 'key_compare_func');

print_r($result);

Output:

Array
(
    [a] => 100
    [b] => 200
    [C] => 300
)

Example 3: Filtering Arrays Based on Prefix in Keys

Filter two arrays to find common keys starting with a specific prefix, using a custom comparison function.

function prefix_compare($key1, $key2) {
    if (strpos($key1, 'pre_') === 0 && $key1 === $key2) {
        return 0;
    }
    return $key1 >= $key2 ? 1 : -1;
}

$array1 = array('pre_first' => 'apple', 'pre_second' => 'banana', 'post_third' => 'cherry');
$array2 = array('pre_first' => 'apple', 'second' => 'banana', 'third' => 'cherry');

$result = array_intersect_ukey($array1, $array2, 'prefix_compare');

print_r($result); 

Output:

Array
(
    [pre_first] => apple
)

Subhendu Mohapatra

Author

🎥 Join me live on YouTube

Passionate about coding and teaching, I publish practical tutorials on PHP, Python, JavaScript, SQL, and web development. My goal is to make learning simple, engaging, and project‑oriented with real examples and source code.

← Subscribe to our YouTube Channel here