PMA\libraries\Encoding::convertString PHP Method

    public static function convertString($src_charset, $dest_charset, $what)
    {
        if ($src_charset == $dest_charset) {
            return $what;
        }
        if (is_null(self::$_engine)) {
            self::initEngine();
        }
        switch (self::$_engine) {
            case self::ENGINE_RECODE:
                return recode_string($src_charset . '..' . $dest_charset, $what);
            case self::ENGINE_ICONV:
                return iconv($src_charset, $dest_charset . (isset($GLOBALS['cfg']['IconvExtraParams']) ? $GLOBALS['cfg']['IconvExtraParams'] : ''), $what);
            case self::ENGINE_MB:
                return mb_convert_encoding($what, $dest_charset, $src_charset);
            default:
                return $what;
        }
    }

 public function testMbstring()
 {
     if (!@function_exists('mb_convert_encoding')) {
         $this->markTestSkipped('mbstring extension missing');
     }
     Encoding::setEngine(Encoding::ENGINE_MB);
     $this->assertEquals("This is the Euro symbol '?'.", Encoding::convertString('UTF-8', 'ISO-8859-1', "This is the Euro symbol '€'."));
 }