title: Symfony 4 Parse Error: vendor/symfony/flex/src/Flex.php line 275
body: <p>I am currently using Symfony 4 and while I am trying to create a user login form for my app, I use the command Composer require security and I get this error: </p>
  
  <pre>
  Parse error: parse error in /Applications/MAMP/htdocs/myapp/vendor/symfony/flex/src/Flex.php on line 275
  </pre>
  
  <p>The culprit is in the symfony flex file Flex.php</p>
  
  <pre>$installContribs = $this->composer->getPackage()->getExtra()['symfony']['allow-contrib'] ?? false;</pre>
  
  <p>I then found I cannot use any Composer commands, such as composer update, composer require, and so on. Any help would be appreciated!</p>