XLSXWriter::setSharedString PHP Method

    protected function setSharedString($v)
    {
        if (isset($this->shared_strings[$v])) {
            $string_value = $this->shared_strings[$v];
        } else {
            $string_value = count($this->shared_strings);
            $this->shared_strings[$v] = $string_value;
        }
        $this->shared_string_count++;
        //non-unique count
        return $string_value;
    }