How to send Extra parameters in payload via Amazon SNS Push Notification on Android

I am using Amazon SNS Push notifications service to send push notifications to Android Devices. I am trying to send variables in the array

array(
        'TopicArn' => 'TopicARN',
        'Message' => '{
                        "default": "This is a simple message",
                        "GCM": "{ \"data\": { \"message\": \"$helloWorld\"},\"time_to_live\": 10,\"collapse_key\":\"$msg_Title\"} }"
                     }'
                     'Subject' => 'Simple Messaging',
                     'MessageStructure' => 'json'
));

I am trying to send multiple messages using SQL as well, but I is just sending the Variables as string.

Please Help.