Remember that declaring a tick handler can become really expensive in terms of CPU cycles: Every n ticks the signal handling overhead will be executed.
So instead of declaring tick=1, test if tick=100 can do the job. If so, you are likely to gain fivefold speed.
As your script might always might miss some signals due to blocking operations like cURL downloads, call pcntl_signal_dispatch() on vital spots, e.g. at the beginning of your main loop.