TCPDFBarcode::barcode_code39 PHP Method

    protected function barcode_code39($code, $extended = false, $checksum = false)
    {
        $chr['0'] = '111331311';
        $chr['1'] = '311311113';
        $chr['2'] = '113311113';
        $chr['3'] = '313311111';
        $chr['4'] = '111331113';
        $chr['5'] = '311331111';
        $chr['6'] = '113331111';
        $chr['7'] = '111311313';
        $chr['8'] = '311311311';
        $chr['9'] = '113311311';
        $chr['A'] = '311113113';
        $chr['B'] = '113113113';
        $chr['C'] = '313113111';
        $chr['D'] = '111133113';
        $chr['E'] = '311133111';
        $chr['F'] = '113133111';
        $chr['G'] = '111113313';
        $chr['H'] = '311113311';
        $chr['I'] = '113113311';
        $chr['J'] = '111133311';
        $chr['K'] = '311111133';
        $chr['L'] = '113111133';
        $chr['M'] = '313111131';
        $chr['N'] = '111131133';
        $chr['O'] = '311131131';
        $chr['P'] = '113131131';
        $chr['Q'] = '111111333';
        $chr['R'] = '311111331';
        $chr['S'] = '113111331';
        $chr['T'] = '111131331';
        $chr['U'] = '331111113';
        $chr['V'] = '133111113';
        $chr['W'] = '333111111';
        $chr['X'] = '131131113';
        $chr['Y'] = '331131111';
        $chr['Z'] = '133131111';
        $chr['-'] = '131111313';
        $chr['.'] = '331111311';
        $chr[' '] = '133111311';
        $chr['$'] = '131313111';
        $chr['/'] = '131311131';
        $chr['+'] = '131113131';
        $chr['%'] = '111313131';
        $chr['*'] = '131131311';
        $code = strtoupper($code);
        if ($extended) {
            // extended mode
            $code = $this->encode_code39_ext($code);
        }
        if ($code === false) {
            return false;
        }
        if ($checksum) {
            // checksum
            $code .= $this->checksum_code39($code);
        }
        // add start and stop codes
        $code = '*' . $code . '*';
        $bararray = array('code' => $code, 'maxw' => 0, 'maxh' => 1, 'bcode' => array());
        $k = 0;
        $clen = strlen($code);
        for ($i = 0; $i < $clen; ++$i) {
            $char = $code[$i];
            if (!isset($chr[$char])) {
                // invalid character
                return false;
            }
            for ($j = 0; $j < 9; ++$j) {
                if ($j % 2 == 0) {
                    $t = true;
                    // bar
                } else {
                    $t = false;
                    // space
                }
                $w = $chr[$char][$j];
                $bararray['bcode'][$k] = array('t' => $t, 'w' => $w, 'h' => 1, 'p' => 0);
                $bararray['maxw'] += $w;
                ++$k;
            }
            // intercharacter gap
            $bararray['bcode'][$k] = array('t' => false, 'w' => 1, 'h' => 1, 'p' => 0);
            $bararray['maxw'] += 1;
            ++$k;
        }
        return $bararray;
    }