case-insensitive array_unique

I'm trying to write a few lines of code to make a case insensitive array unique type function. Here's what I have so far:

foreach ($topics as $value) {
    $lvalue = strtolower($value);
    $uvalue = strtolower($value);

    if (in_array($value, $topics) == FALSE || in_array($lvalue, $topics) == FALSE || in_array($uvalue, $topics) == FALSE) {
        array_push($utopics, $value);
    }
}

The trouble is the if statement. I think there's something wrong with my syntax, but I'm relatively new to PHP and I'm not sure what it is. Any help?