php array_iunique不区分大小写没有拉丁值

Hello I have string that might include duplicate strings-words for example "Το το" So far what I have is this:

function array_iunique($array) {
    return array_intersect_key($array,array_unique(array_map('mb_strtolower',$array)));
}

array_iunique

When i test with a string in English like "To to" it works great and outputs an array with 1 value, but when I try it with the Greek string mentioned above it doesn't. What am I missing here ?

Expected result would be to return only 1 word and I'm interested in Greek only.

For anyone that might have the same issue this solves the issue:

function array_iunique($array) {
    return array_intersect_key(
        $array,
        array_unique(
            array_map(
                function($text) {
                    return mb_strtolower($text, 'UTF-8');
                },
                $array
            )
        )
    );
}

ref