Composer需要phpoffice / phpspreadsheet不起作用

我想使用包Phpspreadsheet编写脚本.我不是 PHP的经验.我试图通过sudo composer需要phpoffice / phpspreadsheet添加对我的脚本的引用.但它不起作用.我收到错误：在stallation失败,删除composer.json ….如果不知道为什么它不工作.任何的想法？

详细错误：

Your requirements could not be resolved to an installable set of packages.

Problem 1
- Installation request for phpoffice/phpspreadsheet ^1.0 -> satisfiable by phpoffice/phpspreadsheet[1.0.0].
- phpoffice/phpspreadsheet 1.0.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.

To enable extensions,verify that they are enabled in those .ini files:
- /etc/php/7.0/cli/php.ini
- /etc/php/7.0/cli/conf.d/10-mysqlnd.ini
- /etc/php/7.0/cli/conf.d/10-opcache.ini
- /etc/php/7.0/cli/conf.d/10-pdo.ini
- /etc/php/7.0/cli/conf.d/20-calendar.ini
- /etc/php/7.0/cli/conf.d/20-ctype.ini
- /etc/php/7.0/cli/conf.d/20-exif.ini
- /etc/php/7.0/cli/conf.d/20-fileinfo.ini
- /etc/php/7.0/cli/conf.d/20-ftp.ini
- /etc/php/7.0/cli/conf.d/20-gettext.ini
- /etc/php/7.0/cli/conf.d/20-iconv.ini
- /etc/php/7.0/cli/conf.d/20-json.ini
- /etc/php/7.0/cli/conf.d/20-mcrypt.ini
- /etc/php/7.0/cli/conf.d/20-mysqli.ini
- /etc/php/7.0/cli/conf.d/20-pdo_mysql.ini
- /etc/php/7.0/cli/conf.d/20-phar.ini
- /etc/php/7.0/cli/conf.d/20-posix.ini
- /etc/php/7.0/cli/conf.d/20-readline.ini
- /etc/php/7.0/cli/conf.d/20-shmop.ini
- /etc/php/7.0/cli/conf.d/20-sockets.ini
- /etc/php/7.0/cli/conf.d/20-sysvmsg.ini
- /etc/php/7.0/cli/conf.d/20-sysvsem.ini
- /etc/php/7.0/cli/conf.d/20-sysvshm.ini
- /etc/php/7.0/cli/conf.d/20-tokenizer.ini
You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.

Installation failed,reverting ./composer.json to its original content.