You can use this function to fix problems related to Turkish "ı", "I", "i", "İ" characters. This function also replaces the weird "i̇" character with regular "i" character ("i̇ => i").
function mb_convert_case_tr($str, $type, $encoding = "UTF-8")
{
switch ($type) {
case "u":
case "upper":
case MB_CASE_UPPER:
$type = MB_CASE_UPPER;
break;
case "l":
case "lower":
case MB_CASE_LOWER:
$type = MB_CASE_LOWER;
break;
case "t":
case "title":
case MB_CASE_TITLE:
$type = MB_CASE_TITLE;
break;
}
$str = str_replace("i", "İ", $str);
$str = str_replace("I", "ı", $str);
$str = mb_convert_case($str, $type, $encoding);
$str = str_replace("i̇", "i", $str);
return $str;
}
