Composer wrapper problems

I just ran ./scripts/composer_wrapper.php install --no-dev and then my output was:

 Loading composer repositories with package information
Installing dependencies from lock file
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for erusev/parsedown 1.7.1 -> satisfiable by erusev/parsedown[1.7.1].
    - erusev/parsedown 1.7.1 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
  Problem 2
    - Installation request for laravel/framework v5.4.36 -> satisfiable by laravel/framework[v5.4.36].
    - laravel/framework v5.4.36 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
  Problem 3
    - laravel/framework v5.4.36 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
    - wpb/string-blade-compiler 3.4.x-dev requires laravel/framework 5.4.* -> satisfiable by laravel/framework[v5.4.36].
    - Installation request for wpb/string-blade-compiler 3.4.x-dev -> satisfiable by wpb/string-blade-compiler[3.4.x-dev].

  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/15-xml.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-curl.ini
    - /etc/php/7.0/cli/conf.d/20-dom.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-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-simplexml.ini
    - /etc/php/7.0/cli/conf.d/20-snmp.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-wddx.ini
    - /etc/php/7.0/cli/conf.d/20-xmlreader.ini
    - /etc/php/7.0/cli/conf.d/20-xmlwriter.ini
    - /etc/php/7.0/cli/conf.d/20-xsl.ini
  You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.

Any help would be appreciated I’m not really sure what went wrong. I had an issue and it wanted me to install composer when I ran ./validate.php so I ran an apt-get install composer, then this popped up after running the above command. Do I need to change something in a config file somewhere or do I need to change all these files?

looks like your missing mbstring try

sudo apt-get install php7.0-mbstring

or

sudo yum install php70w-mbstring

Then re-run the script

./scripts/composer_wrapper.php install --no-dev