I have been searching all over the web and nothing gives a clear answer to confirm the subscription request from amazon SNS. I already send the subscription from the amazon console to my website, but what's next? I am using amazon EC2 as my server with PHP.
Before you even configure the HTTP/HTTPS endpoint subscription through AWS management console, you need to make sure that the HTTP or HTTPS endpoint of your PHP web site has the capability to handle the HTTP POST requests that Amazon SNS generates. There are several types of SNS messages: SubscriptionConfirmation, Notification and UnsubscribeConfirmation. Your PHP code needs to get the header x-amz-sns-message-type from request and process it based on the message type. For SubscriptionConfirmation message, your PHP application needs to process the POST message body, which is a JSON document. In order to subscribe the topic, your PHP code needs to visit the "SubscriberURL" specified in the JSON body. Optionally, you should verify the signature to make sure the authenticity of message before subscribing the topic.
You can find more details on AWS documentation: http://docs.aws.amazon.com/sns/latest/dg/SendMessageToHttp.html