我正在尝试在Ubuntu PC上使用composer安装laravel安装程序，但是在安装过程中出现此错误。您的要求无法解决为一组可安装的软件包。

  Problem 1
    - laravel/installer v1.4.1 requires ext-zip * -> the requested PHP extension zip is missing from your system.
    - laravel/installer v1.4.0 requires ext-zip * -> the requested PHP extension zip is missing from your system.
    - Installation request for laravel/installer ^1.4 -> satisfiable by laravel/installer[v1.4.0, v1.4.1].

  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-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-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.
`

出现错误，然后我使用此注释：

composer global require "laravel/installer"