to find the text width in Zend pdf

 private function getTextWidth($text, Zend_Pdf_Resource_Font $font, $font_size)
    {
        $drawing_text = iconv('', 'UTF-16BE', $text);
        $characters    = array();
        for ($i = 0; $i < strlen($drawing_text); $i++) {
            $characters[] = (ord($drawing_text[$i++]) << 8) | ord ($drawing_text[$i]);
        }
        $glyphs        = $font->glyphNumbersForCharacters($characters);
        $widths        = $font->widthsForGlyphs($glyphs);
        $text_width   = (array_sum($widths) / $font->getUnitsPerEm()) * $font_size;
        return $text_width;
    }