title: FCM verify device token before sending push notification using PHP
body: <p>I have fcm tokens in my database and for some tokens are used to send push notifications.</p>
  
  <p>Everything is working fine as required.
  But there is optimization required since some device token I am getting </p>
  
  <pre><code>string(116)
  "{
  "multicast_id": 1234,
  "success": 0,
  "failure": 1,
  "canonical_ids": 0,
  "results": [{
    "error": "NotRegistered"
  }]
  }
  "
  </code></pre>
  
  <p>Could any help me verify device token if registered already before sending push notification? </p>