Gas hob clicking

It sounds like the igniter circuit is in parallel any knob turned on fires the circuit. If only one ring sparked in the past the control module may have failed. One of the switches to start the igniter may be stuck with grease and oil or a wire may have shorted causing the problem. Removing the knob and looking for a lever or switch contact may show what the problem is. If All the levers work a broken switch or failed control unit may be the cause but many times the problem can be found with a visual inspection.