array_diff_ukey(): Difference between two arrays comparing keys through callback function

$new_array = array_diff_ukey ($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('One'=> 'First','Fourth','2nd');

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

Two -> Second 
Three -> Third 

Example 2

function my_function($a, $b) {
    static $match = [
        'First' => 'One',
        'Second' => 'Two',
        'Third' => 'Three',
        'Fourth' => 'Four',
        'Fifth' => 'five'
    ];
    if (isset($match[$a])) {
        return $match[$a] != $b;
    } elseif(isset($match[$b])) {
        return $match[$b] != $a; 
    }
    return true; 
// 0 returned if there is a match and 1 if no match 
}

$first=array('First' =>1,'Second'=>2,'Third'=>33,'FourthH'=>4,'Fifth'=>5);
$second=array('One'=>1,'Two'=>2,'Three'=>3,'Four'=>4);
$result=array_diff_ukey($first,$second,"my_function");
while (list ($key, $val) = each ($result)) {
echo "$key -> $val <br>";
}

FourthH -> 4 
Fifth -> 5

Example 2: Case-Insensitive Key Comparison

You can use array_diff_ukey() to perform case-insensitive key comparison by defining a custom comparison function:

$arr1 = array("Key1" => 1, "Key2" => 2);
$arr2 = array("key1" => 1, "key3" => 3);

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

$result = array_diff_ukey($arr1, $arr2, "caseInsensitiveCompare");
print_r($result); // Outputs: Array ( [Key2] => 2 )