CronLingo\Parser::lex PHP Method

    protected function lex($string)
    {
        $delimiter = ' ';
        $fragment = strtok($string, $delimiter);
        $regex = $this->compileRegex();
        $tokens = array();
        while (false !== $fragment) {
            if (preg_match($regex, $fragment, $matches)) {
                foreach ($matches as $offset => $val) {
                    if (!empty($val) && $offset > 0) {
                        $token = array_values($this->tokenMap)[$offset - 1];
                        $tokens[] = array('token' => $token, 'value' => strtolower($matches[0]));
                    }
                }
            }
            $fragment = strtok($delimiter);
        }
        return $tokens;
    }