(PECL hrtime >= 0.4.3) Whether the measurement is running.
(PECL hrtime >= 0.4.3) Get elapsed ticks for the last interval.
(PECL hrtime >= 0.4.3) Stop time measurement
(PECL hrtime >= 0.4.3) Start time measurement
(PECL hrtime >= 0.4.3) Timer frequency in ticks per second
(PECL hrtime >= 0.4.3) Get elapsed ticks for all intervals.