Can I make web interface for hardware events?

You go down a different route...

1. Set all driving pins to same state
   
2. Set all sensing pins in state with single watch
   
3. Single watch triggers a 'complete' scan to multiplex drive/sense the key
   
4. Decide valid key (combination press) and perform action based on key
   
5. Set all driving pins to same state
   
6. Set all sensing pins in state with single watch on opposite edge
   
7. Single watch triggers return to original state (1 and 2).
   
   

If you want to have a repeat on holding a key longer than a configurable time, you need to modify 4 a bit and have a logical loop (timout before you check again with a scan), then move on.

For sure fall NOT into the arduino trap. (Check out the similarly structured approach I took with the touch screen and its application with a UI...).