I have a problem installing laravel on ubuntu

Question

I just installed ubuntu on my laptop and I am installing laravel but I get this error when I run the "composer update" command

I need to fix the problem in order to continue with my project

Install Php7.2-cli and postgres and composer global require laravel / installer also apache2

Problem 1
    - laravel/framework v5.8.9 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.8 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.7 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.6 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.5 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.4 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.30 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.3 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.29 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.28 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.27 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.26 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.25 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.24 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.23 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.22 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.21 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.20 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.2 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.19 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.18 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.17 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.16 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.15 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.14 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.13 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.12 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.11 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.10 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.1 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework v5.8.0 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - laravel/framework 5.8.x-dev requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - Installation request for laravel/framework 5.8.* -> satisfiable by laravel/framework[5.8.x-dev, v5.8.0, v5.8.1, v5.8.10, v5.8.11, v5.8.12, v5.8.13, v5.8.14, v5.8.15, v5.8.16, v5.8.17, v5.8.18, v5.8.19, v5.8.2, v5.8.20, v5.8.21, v5.8.22, v5.8.23, v5.8.24, v5.8.25, v5.8.26, v5.8.27, v5.8.28, v5.8.29, v5.8.3, v5.8.30, v5.8.4, v5.8.5, v5.8.6, v5.8.7, v5.8.8, v5.8.9].


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-opcache.ini
    - /etc/php/7.2/cli/conf.d/10-pdo.ini
    - /etc/php/7.2/cli/conf.d/15-xml.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-dom.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-pdo_pgsql.ini
    - /etc/php/7.2/cli/conf.d/20-pgsql.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-simplexml.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-wddx.ini
    - /etc/php/7.2/cli/conf.d/20-xmlreader.ini
    - /etc/php/7.2/cli/conf.d/20-xmlwriter.ini
    - /etc/php/7.2/cli/conf.d/20-xsl.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

You are missing the mbstring in your SO:

Install the package:

sudo apt-get install php7.2-mbstring

Restart Server:

sudo service apache2 restart
or
sudo service nginx restart

Now you should see mbstring as enabled in a file with below code:

<?php echo phpinfo(); ?>