code: function EncodeQP ($str) {
          $encoded = $this->FixEOL($str);
          if (substr($encoded, -(strlen($this->LE))) != $this->LE)
              $encoded .= $this->LE;
  
          // Replace every high ascii, control and = characters
          $encoded = preg_replace('/([\000-\010\013\014\016-\037\075\177-\377])/e',
                    "'='.sprintf('%02X', ord('\\1'))", $encoded);
          // Replace every spaces and tabs when it's the last character on a line
          $encoded = preg_replace("/([\011\040])".$this->LE."/e",
                    "'='.sprintf('%02X', ord('\\1')).'".$this->LE."'", $encoded);
  
          // Maximum line length of 76 characters before CRLF (74 + space + '=')
          $encoded = $this->WrapText($encoded, 74, true);
  
          return $encoded;
      }
docs: Encode string to quoted-printable.
  @access private
  @return string