Установка Laravel на сервере)

composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.
 
  Problem 1
    - phpunit/phpunit 7.0.0 requires phpunit/php-code-coverage ^6.0 -> satisfiable by phpunit/php-code-coverage[6.0.0, 6.0.1, 6.0.x-dev].
    - phpunit/phpunit 7.0.1 requires phpunit/php-code-coverage ^6.0 -> satisfiable by phpunit/php-code-coverage[6.0.0, 6.0.1, 6.0.x-dev].
    - phpunit/phpunit 7.0.2 requires phpunit/php-code-coverage ^6.0 -> satisfiable by phpunit/php-code-coverage[6.0.0, 6.0.1, 6.0.x-dev].
    - phpunit/phpunit 7.0.x-dev requires phpunit/php-code-coverage ^6.0 -> satisfiable by phpunit/php-code-coverage[6.0.0, 6.0.1, 6.0.x-dev].
    - phpunit/phpunit 7.1.x-dev requires phpunit/php-code-coverage ^6.0 -> satisfiable by phpunit/php-code-coverage[6.0.0, 6.0.1, 6.0.x-dev].
    - phpunit/php-code-coverage 6.0.x-dev requires ext-xmlwriter * -> the requested PHP extension xmlwriter is missing from your system.
    - phpunit/php-code-coverage 6.0.1 requires ext-xmlwriter * -> the requested PHP extension xmlwriter is missing from your system.
    - phpunit/php-code-coverage 6.0.0 requires ext-xmlwriter * -> the requested PHP extension xmlwriter is missing from your system.
    - Installation request for phpunit/phpunit ^7.0 -> satisfiable by phpunit/phpunit[7.0.0, 7.0.1, 7.0.2, 7.0.x-dev, 7.1.x-dev].
 
  To enable extensions, verify that they are enabled in your .ini files:
    - /opt/php71/etc/php.ini
    - /opt/php71/etc/php.d/10-mysqlnd.ini
    - /opt/php71/etc/php.d/10-pdo.ini
    - /opt/php71/etc/php.d/20-curl.ini
    - /opt/php71/etc/php.d/20-dom.ini
    - /opt/php71/etc/php.d/20-gd.ini
    - /opt/php71/etc/php.d/20-json.ini
    - /opt/php71/etc/php.d/20-mbstring.ini
    - /opt/php71/etc/php.d/20-mcrypt.ini
    - /opt/php71/etc/php.d/20-mysqli.ini
    - /opt/php71/etc/php.d/20-pdo_mysql.ini
    - /opt/php71/etc/php.d/20-soap.ini
    - /opt/php71/etc/php.d/20-xmlrpc.ini
    - /opt/php71/etc/php.d/pdo_dblib.ini
    - /opt/php71/etc/php.d/pdo_sqlite.ini
    - /opt/php71/etc/php.d/xmlreader.ini
    - /opt/php71/etc/php.d/xsl.ini
    - /opt/php71/etc/php.d/zip.ini
  You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.