title: Updating Composer in Digital Ocean Ubuntu via Terminal errors
body: <p>I am using a mac and in the command line, I am logged into the server, and want to install composer however I get a number of issues (see below). I don't need PHP unit and so I have also tried <code>composer install --no-dev</code> but the same errors are appearing. Any idea or solution? </p>
  
  <pre><code>Warning: The lock file is not up to date with the latest changes in composer.json. You may be getting outdated dependencies. It is recommended that you run `composer update` or `composer update &lt;package name&gt;`.
  Your requirements could not be resolved to an installable set of packages.
  
    Problem 1
      - Installation request for tijsverkoyen/css-to-inline-styles 2.2.2 -&gt; satisfiable by tijsverkoyen/css-to-inline-styles[2.2.2].
      - tijsverkoyen/css-to-inline-styles 2.2.2 requires ext-dom * -&gt; the requested PHP extension dom is missing from your system.
    Problem 2
      - tijsverkoyen/css-to-inline-styles 2.2.2 requires ext-dom * -&gt; the requested PHP extension dom is missing from your system.
      - laravel/framework v7.3.0 requires tijsverkoyen/css-to-inline-styles ^2.2.2 -&gt; satisfiable by tijsverkoyen/css-to-inline-styles[2.2.2].
      - Installation request for laravel/framework v7.3.0 -&gt; satisfiable by laravel/framework[v7.3.0].
  </code></pre>
  
  <p>I also tried to install the tijsverkoyen via Sudo and receive another list of issues </p>
  
  <pre><code>Problem 1
      - phpunit/phpunit 8.5.x-dev requires ext-dom * -&gt; the requested PHP extension dom is missing from your system.
      - phpunit/phpunit 8.5.3 requires ext-dom * -&gt; the requested PHP extension dom is missing from your system.
      - phpunit/phpunit 8.5.2 requires ext-dom * -&gt; the requested PHP extension dom is missing from your system.
      - phpunit/phpunit 8.5.1 requires ext-dom * -&gt; the requested PHP extension dom is missing from your system.
      - phpunit/phpunit 8.5.0 requires ext-dom * -&gt; the requested PHP extension dom is missing from your system.
      - Installation request for phpunit/phpunit ^8.5 -&gt; satisfiable by phpunit/phpunit[8.5.0, 8.5.1, 8.5.2, 8.5.3, 8.5.x-dev].
  </code></pre>