composer.json

{
    "require": {
        "symfony/symfony": "^4.0"
    },
    "minimum-stability": "dev"
}

gistfile1.txt

$ composer install
Loading composer repositories with package information
Updating dependencies (including require-dev)
Package operations: 18 installs, 0 updates, 0 removals
  - Installing symfony/polyfill-mbstring (dev-master 25b83a5): Cloning 25b83a5050 from cache
  - Installing symfony/polyfill-ctype (dev-master 9d31bef): Cloning 9d31bef82d from cache
  - Installing twig/twig (2.x-dev 53ca200): Cloning 53ca200b96 from cache
  - Installing symfony/polyfill-php72 (dev-master a4576e2): Cloning a4576e282d from cache
  - Installing psr/simple-cache (dev-master 408d5ea): Cloning 408d5eafb8 from cache
  - Installing psr/log (dev-master 3490ba5): Cloning 3490ba5925 from cache
  - Installing psr/link (dev-master 131b5c3): Cloning 131b5c337d from cache
  - Installing psr/container (dev-master 2cc4a01): Cloning 2cc4a01788 from cache
  - Installing psr/cache (dev-master 78c5a01): Cloning 78c5a01ddb from cache
  - Installing fig/link-util (dev-master 1a07821): Cloning 1a07821801 from cache
  - Installing doctrine/lexer (dev-master c0970c7): Cloning c0970c7889 from cache
  - Installing doctrine/inflector (dev-master 8289057): Cloning 8289057266 from cache
  - Installing doctrine/collections (dev-master 33407e4): Cloning 33407e41a3 from cache
  - Installing doctrine/cache (dev-master 280484a): Cloning 280484a92e from cache
  - Installing doctrine/annotations (1.7.x-dev 232c5da): Cloning 232c5da390 from cache
  - Installing doctrine/common (dev-master 44d1cb5): Cloning 44d1cb5cfc from cache
  - Installing symfony/symfony (dev-master 50c4384): Cloning 50c4384caf from cache
  - Installing symfony/polyfill-intl-icu (dev-master 80ee17a): Cloning 80ee17ae83 from cache
doctrine/cache suggests installing alcaeus/mongo-php-adapter (Required to use legacy MongoDB driver)
Writing lock file
Generating autoload files