Leafo\ScssPhp\Compiler::libStrSlice PHP Method

    protected function libStrSlice($args)
    {
        if (isset($args[2]) && $args[2][1] == 0) {
            return static::$nullString;
        }
        $string = $this->coerceString($args[0]);
        $stringContent = $this->compileStringContent($string);
        $start = (int) $args[1][1];
        if ($start > 0) {
            $start--;
        }
        $end = (int) $args[2][1];
        $length = $end < 0 ? $end + 1 : ($end > 0 ? $end - $start : $end);
        $string[2] = $length ? [substr($stringContent, $start, $length)] : [substr($stringContent, $start)];
        return $string;
    }