title: How to create and use environment variable .env yii2
body: <p>I want to create a file .env:</p>
  
  <pre><code> FACEBOOK_CLIENT_ID=*****
   FACEBOOK_CLIENT_SECRET=*****
  </code></pre>
  
  <p>and use variable for config </p>
  
  <pre><code>'facebook' =&gt; [
                  'class' =&gt; 'yii\authclient\clients\Facebook',
                  'clientId' =&gt; env('FACEBOOK_CLIENT_ID'),
                  'clientSecret' =&gt; env('FACEBOOK_CLIENT_SECRET'),
              ],
  </code></pre>