PHP array_​diff_​ukey() Function

The array_​diff_​ukey() function is an inbuilt function in PHP that is used to execute the difference of arrays by using a callback function on the keys for comparison. This function compares the key from the array against the keys from arrays and returns the difference of that.

Syntax:

array array_diff_ukey(array $array, 
    array ...$arrays, callable $key_compare_func)

Parameters: This function accepts the following parameters that are described below:

• $array: This parameter holds the array to compare from.
• $arrays: This parameter holds the arrays to compare against.
• $key_compare_func: It is a comparison callback function that returns an integer value based on the arguments.

Return Value: This function returns an array that contains all the entries from an array and is not present in any other arrays.

Example 1:

PHP

<?php

function key_compare_func($key1, $key2) {
    if ($key1 == $key2)
        return 0;
    else if ($key1 > $key2)
        return 1;
    else
        return -1;
}

$arr1 = array(
    'A'  => 15,
    'B'  => 12,
    'C'  => 34,
    'D' => 14
);

$arr2 = array(
    'B' => 50,
    'D' => 60,
    'E' => 70,
    'F'   => 80
);

var_dump(array_diff_ukey($arr1, $arr2, 'key_compare_func'));
?>

Output:

array(2) {
      ["A"] => int(15)
      ["C"] => int(34)
}

Example 2:

PHP

<?php

function key_compare_func($key1, $key2) {
    if ($key1 == $key2)
        return 0;
    else if ($key1 < $key2)
        return 1;
    else
        return -1;
}

$arr1 = array(
    'Geeks'  => "HTML",
    'GFG'  => "CSS",
    'Geek'  => "JavaScript",
    'G4G' => "PHP"
);

$arr2 = array(
    'Geeks' => "CPP",
    'G4G' => "Java",
    'Geek' => "Python",
    'GeeksforGeeks'   => "DSA"
);

var_dump(array_diff_ukey($arr1, $arr2, 'key_compare_func'));
?>

Output:

array(1) {
      ["GFG"] => string(3) "CSS"
}

Reference: https://www.php.net/manual/en/function.array-diff-ukey.php