新安装的laravel上的依赖关系冲突

Question

我一直在尝试使用laravel composer CLI创建一个新项目，但没有成功……

当我尝试创建它时，我得到了以下错误：

➜  larapjs export PATH="$PATH:$HOME/.composer/vendor/bin"
➜  larapjs laravel new testp
Crafting application...
Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for phpunit/php-code-coverage 4.0.8 -> satisfiable by phpunit/php-code-coverage[4.0.8].
    - phpunit/php-code-coverage 4.0.8 requires ext-dom * -> the requested PHP extension dom is missing from your system.
  Problem 2
    - Installation request for phpunit/phpunit 5.7.20 -> satisfiable by phpunit/phpunit[5.7.20].
    - phpunit/phpunit 5.7.20 requires ext-dom * -> the requested PHP extension dom is missing from your system.

  To enable extensions, verify that they are enabled in your .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-gd.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-mbstring.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
    - /etc/php/7.0/cli/conf.d/20-zip.ini
  You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.
Application ready! Build something amazing.

由于我是composer的新手，我不知道从哪里开始解决这个冲突问题。

如有任何建议，我们将不胜感激。