Filter characters more than three bytes in UTF8 characters, or non-UTF8 characters

/** *  filter for 3 bytes inside utf8 *  @param   $str  *  @return  string */function  FilterUtf8 ($STR) {    /*utf8  encoding table:     * unicode symbol range             | utf-8 Encoding Method     *  u0000 0000 - u0000 007f   | 0xxxxxxx    *  u0000 0080 - u0000 07ff   | 110xxxxx 10xxxxxx     * u0000 0800 - u0000 FFFF   | 1110xxxx 10xxxxxx  10xxxxxx    *    */     $re  =  ';      $str  = str_split (Bin2Hex ($STR),  2);     $mo  =   1<<7;     $mo 2 =  $mo  |  (1 << 6);      $mo 3 =  $mo 2 |  (1 << 5);          //three bytes       $mo 4 =  $mo 3 |  (1 << 4);           //four bytes      $mo 5 =  $mo 4 |  (1 << &NBSP;3);           //Five bytes      $mo 6 =   $mo 5 |  (1 << 2);           // Six bytes     for  ($i  = 0;  $i  < count ($str);  $i + +)      {        if  (Hexdec ($str [$i])  &  ($MO))  == 0)         {              $re  .=  chr (Hexdec ($str [$i]);             continue;        }         //4 bytes   and above         if  ((Hexdec ($str [$i])  &  ($mo 6)  )   ==  $mo 6)         {              $i  =  $i  +5;             continue;         }        if  (Hexdec ($str [$i])  &  ($mo 5)   )   ==  $mo 5)         {              $i  =  $i  +4;             continue;        }         if  ((Hexdec ($str [$i])  &  ($mo 4)  )   ==  $mo 4)          {             $i  =  $i  +3;            continue;         }        if  ( Hexdec ($str [$i]  &  ($mo 3)  )   ==  $mo 3 )          {             $i  =  $i  +2;            if  ((Hexdec ($str [$i])  &  ($MO)  )   ==  $mo)  &&   ((Hexdec ($str [$i  -  1])  &  ($MO)  )   ==  $mo)   )              {                 $r  =  Chr (Hexdec ($str [$i  - 2]) .             &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;CHR (Hexdec ($str [$i  - 1]) .     &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;CHR (Hexdec ($ str[$i]);                 $re  .=  $r;            }             continue;         }        if  (Hexdec ($str [$i])  &  ($mo 2)   )   ==  $mo 2 )         {              $i  =  $i  +1;             if  (Hexdec ($str [$i])  &  ($MO)  )   ==  $mo)              {                  $re  .= chr (Hexdec ($str [$i  - 1]) &NBSP;.&NBSP;CHR (Hexdec ($str [$i]));            }             continue;         }    }    return  $re;}

Filter characters more than three bytes in UTF8 characters, or non-UTF8 characters