title: Undefined class constant 'VERSION' when using kreait/firebase-php
body: <p>I am getting the following error when try to send push notification to mobile app using FCM from my PHP application. </p>
  
  <blockquote>
    <p>Undefined class constant 'VERSION'</p>
    
    <p>file- /usr/share/nginx/html/project-folder/vendor/kreait/firebase-php/src/Firebase/Exception/MessagingApiExceptionConverter.php</p>
  </blockquote>
  
  <p><a href="https://github.com/kreait/firebase-php" rel="nofollow noreferrer">kreait/firebase-php</a> is being used.</p>