title: Composer install & update issue (requires php ^7.0 -> your php version (8.0.3))
body: <p>We are starting to use PHP 8 on new projects. But we are also migrating old projects to the new PHP 8. Problems occur when installing dependencies.</p>
  <p>Because PHP 8 is relatively new, there are still many third-party packages that depend on older versions of PHP (mostly only due to outdated configuration).</p>
  <p>My PHP version:</p>
  <pre><code>martin@empire:~$ php -v
  PHP 8.0.3 (cli) (built: Mar  5 2021 07:54:13) ( NTS )
  Copyright (c) The PHP Group
  Zend Engine v4.0.3, Copyright (c) Zend Technologies
      with Zend OPcache v8.0.3, Copyright (c), by Zend Technologies
  </code></pre>
  <p>Example of <code>composer install</code> on Symfony project:</p>
  <pre><code>martin@empire:~/projects/twig-example$ composer install
  Installing dependencies from lock file (including require-dev)
  Verifying lock file contents can be installed on current platform.
  Your lock file does not contain a compatible set of packages. Please run composer update.
  
    Problem 1
      - twig/twig is locked to version v2.3.0 and an update of this package was not requested.
      - twig/twig v2.3.0 requires php ^7.0 -&gt; your php version (8.0.3) does not satisfy that requirement.
    Problem 2
      - twig/twig v2.3.0 requires php ^7.0 -&gt; your php version (8.0.3) does not satisfy that requirement.
  ...
  
  </code></pre>
  <p>Example <code>composer update</code> on Laravel 8 project:</p>
  <pre><code>martin@empire:~/projects/collabquest-api$ composer update
  Loading composer repositories with package information
  Updating dependencies
  Your requirements could not be resolved to an installable set of packages.
  
    Problem 1
      - jwilsson/spotify-web-api-php[3.6.0, ..., 3.6.2] require php ^7.0 -&gt; your php version (8.0.3) does not satisfy that requirement.
      - Root composer.json requires jwilsson/spotify-web-api-php ^3.6 -&gt; satisfiable by jwilsson/spotify-web-api-php[3.6.0, 3.6.1, 3.6.2].
  </code></pre>
  <p>What is the best way to deal with this issue and solve this dependency problem?</p>