无法在Ubuntu 18.10 LEMP堆栈上安装Laravel？

Question

When running laravel new I receive all these errors. I understand what they mean, but I'm curious to why this happenes, on windows it all went through fine.

I installed php, how come Ubuntu throws errors? Does it exclude a lot of things from the php installation? I'm not really sure why its causing so much drama, this is the 10th set of errors I've gone through today and I'm worried I've done something majorly wrong.

I followed this for my LEMP stack: https://www.digitalocean.com/community/tutorials/how-to-install-linux-nginx-mysql-php-lemp-stack-ubuntu-18-04

Also, before I can even use the laravel command, I have to run export PATH="~/.composer/vendor/bin:$PATH" every time I open a terminal. Is there a way to fix this?

  Problem 1
    - Installation request for erusev/parsedown v1.7.2 -> satisfiable by erusev/parsedown[v1.7.2].
    - erusev/parsedown v1.7.2 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
  Problem 2
    - Installation request for laravel/framework v5.8.7 -> satisfiable by laravel/framework[v5.8.7].
    - laravel/framework v5.8.7 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
  Problem 3
    - Installation request for phar-io/manifest 1.0.3 -> satisfiable by phar-io/manifest[1.0.3].
    - phar-io/manifest 1.0.3 requires ext-dom * -> the requested PHP extension dom is missing from your system.
  Problem 4
    - Installation request for phpunit/php-code-coverage 6.1.4 -> satisfiable by phpunit/php-code-coverage[6.1.4].
    - phpunit/php-code-coverage 6.1.4 requires ext-dom * -> the requested PHP extension dom is missing from your system.
  Problem 5
    - Installation request for phpunit/phpunit 7.5.7 -> satisfiable by phpunit/phpunit[7.5.7].
    - phpunit/phpunit 7.5.7 requires ext-dom * -> the requested PHP extension dom is missing from your system.
  Problem 6
    - Installation request for theseer/tokenizer 1.1.0 -> satisfiable by theseer/tokenizer[1.1.0].
    - theseer/tokenizer 1.1.0 requires ext-dom * -> the requested PHP extension dom is missing from your system.
  Problem 7
    - laravel/framework v5.8.7 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - beyondcode/laravel-dump-server 1.2.2 requires illuminate/console 5.6.*|5.7.*|5.8.* -> satisfiable by laravel/framework[v5.8.7].
    - Installation request for beyondcode/laravel-dump-server 1.2.2 -> satisfiable by beyondcode/laravel-dump-server[1.2.2].

  To enable extensions, verify that they are enabled in your .ini files:
    - /etc/php/7.2/cli/php.ini
    - /etc/php/7.2/cli/conf.d/10-mysqlnd.ini
    - /etc/php/7.2/cli/conf.d/10-opcache.ini
    - /etc/php/7.2/cli/conf.d/10-pdo.ini
    - /etc/php/7.2/cli/conf.d/20-calendar.ini
    - /etc/php/7.2/cli/conf.d/20-ctype.ini
    - /etc/php/7.2/cli/conf.d/20-exif.ini
    - /etc/php/7.2/cli/conf.d/20-fileinfo.ini
    - /etc/php/7.2/cli/conf.d/20-ftp.ini
    - /etc/php/7.2/cli/conf.d/20-gettext.ini
    - /etc/php/7.2/cli/conf.d/20-iconv.ini
    - /etc/php/7.2/cli/conf.d/20-json.ini
    - /etc/php/7.2/cli/conf.d/20-mbstring.ini
    - /etc/php/7.2/cli/conf.d/20-mysqli.ini
    - /etc/php/7.2/cli/conf.d/20-pdo_mysql.ini
    - /etc/php/7.2/cli/conf.d/20-phar.ini
    - /etc/php/7.2/cli/conf.d/20-posix.ini
    - /etc/php/7.2/cli/conf.d/20-readline.ini
    - /etc/php/7.2/cli/conf.d/20-shmop.ini
    - /etc/php/7.2/cli/conf.d/20-sockets.ini
    - /etc/php/7.2/cli/conf.d/20-sysvmsg.ini
    - /etc/php/7.2/cli/conf.d/20-sysvsem.ini
    - /etc/php/7.2/cli/conf.d/20-sysvshm.ini
    - /etc/php/7.2/cli/conf.d/20-tokenizer.ini
    - /etc/php/7.2/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.

Answer 1

Which PHP version are you using?

You need mbstring extension installed.

Assuming it's PHP7.2, you can install the dependencies required for Laravel like:

sudo apt install php7.2-mbstring php7.2-dom php7.2-pdo php7.2-xml php7.2-common php7.2-bcmath php7.2-json php7.2-cli php7.2-fpm php7.2-mysql

Edit : That LEMP guide doesn't cover php extensions' installation.

Assuimg it's Laravel 5.8, according to the docs , you need some extensions installed, too. Updating my answer accordingly

Note: If you need MySQL etc (because you mentioned LEMP) I've also added php7.2-mysql.

Although, like I mentioned in my comments, I'd prefer Ondrej Sury's PPA and install PHP7.3 and its extensions instead.