How to prevent showing the diamond question mark symbol, even using mb_substr and utf-8

Question

I have read some other questions, tried the answers but got no result at the end. What I get is for example this

Μήπως θα έπρεπε να � ...

and I

Answer 1

Have you tried using these seemingly redundant multibyte safe string functions which are not in the php core?

http://code.google.com/p/mbfunctions/

It appears they offer an mb_strip_tags() function like such:

if (! function_exists('mb_strip_tags'))
{
   function mb_strip_tags($document,$repl = ''){
      $search = array('@]*?>.*?@si',  // Strip out javascript
                     '@<[\/\!]*?[^<>]*?>@si',            // Strip out HTML tags
                     '@]*?>.*?@siU',    // Strip style tags properly
                     '@@'         // Strip multi-line comments including CDATA
      );
      $text = mb_preg_replace($search, $repl, $document);
      return $text;
   }
}