How to delay the execution of a function in php?

Question

PHP

I am writing a bot in php for VK. The task is as follows: the bot writes "Hello", he answers "Bye", but only after 2 hours.
Here is the part of the code that is responsible for sending a response message if they write "Hi".

case strstr($message,'Привет') :
  
   		 $request_params = array( 
   		 	'message' => "Пока", 
   		 	'user_id' => $user_id, 
   		 	'access_token' => $token, 
   		 	'v' => '5.0' 
   		 ); 
   		 $get_params = http_build_query($request_params);

$ch = curl_init(); 
curl_setopt($ch, CURLOPT_URL, 'https://api.vk.com/method/messages.send'); 
curl_setopt($ch, CURLOPT_POST, true); 
curl_setopt($ch, CURLOPT_POSTFIELDS, $get_params);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);curl_close($ch); break;

If everything is left in this form, then everything is fine - the bot works, responds instantly and life is good.
How to force it to do it in an hour/two after reception of the message?
Sleep(10) - works. (but as I understand it, this function causes it to freeze for 10 seconds anywhere in the script)
And if you set it more, then requests begin to pour in several times, the bot can start sending messages 3-4 times.
Which way to think?

Answer 1

Think CRON

Answer 2

Cron or queue servers + workers.

Answer 3

DB + CRON