public function addContent($str, $index = null)
    {
        if (!is_null($index)) {
            $this->contents[$index] = $str;
        } else {
            $this->contents[] = $str;
        }
        return $this;
    }
public function addContent($str, $index = null)
    {
        if (!is_null($index)) {
            $this->contents[$index] = $str;
        } else {
            $this->contents[] = $str;
        }
        return $this;
    }
public function addContent ( $ str , $ index = null ) { if ( ! is_null ( $ index ) ) { $ this -> contents [ $ index ] = $ str ; } else { $ this -> contents [ ] = $ str ; } return $ this ; }
Add a raw content to treat

@param   string      $str    the content to add
@param   null/string $index  the content index
@return self
Add a raw content to treat