Adding fields to notification php object - php

Question

I started developing an app that has push notifications in it. I want my notification object to hold a message and other extra string that I call "color".
Everything worked well until I added the row 'data'=>$color. Now my message field is empty (null) and I can only read the color string.
How to add more data field to the PHP fields array?
function send_notification ($tokens, $message, $color)
{
$url = 'https://fcm.googleapis.com/fcm/send';
$fields = array(
'registration_ids' => $tokens,
'data' => $message,
'data' => $color
);
$headers = array(
'Authorization:key = Not telling you me real key :)',
'Content-Type: application/json'
);
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt ($ch, CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($fields));
$result = curl_exec($ch);
if ($result === FALSE) {
die('Curl failed: ' . curl_error($ch));
}
curl_close($ch);
return $result;
}

Answer 1

You can either change the field name, so it will be like 'color' => $color, or you can append it to the data field. It will be something like this:
$data = $message . "\n";
$data .= $color;
Edit: I believe your $message variabile might be a json, so you should append the $color to that json.