在PHP中实现longpolling的最佳方法是什么？

Question

I want to have the server know when a client disconnects. therefore, I want to implement longpolling. the problem is: the simple solution of looping would consume a lot of resources, but I dont know a better way.

Answer 1

Here's a solution if you want to stay away from WebSockets:

Have the client ping example.php with a unique id every 2 seconds or so.

example.php will do this:

1. Write the current time in seconds, with the filename as the unique id of the client
2. sleep(4)
3. Read the last time written
4. If the difference between the current time, and the last time written is greater than 3 seconds, the user is disconnected. Else, the user is connected.