title: Listen for user inputs on Messenger
body: <p>I'm developing a chatbot on messenger with PHP. I'm not using any 3rd party services like Chatfuel etc.</p>
  
  <p>Whenever, I need a user input, I'm currently storing the question with a key in Redis and sending the response. Then, in the next request, I'm checking if I have that Redis variable stored on my server. Then, I'm processing that user input and deleting the Redis variable.</p>
  
  <p>The problem is that I'm checking for the Redis variables for every webhook request.</p>
  
  <p>Is there any other efficient way to handle the user inputs? I also want to deploy the chatbot on other platforms like Telegram, Skype etc. So, is there a generic event-driven system which would recognise that the incoming webhook request is an answer to a previously asked question?</p>