HRTime &reftitle.intro; The HRTime extension implements a high resolution StopWatch class. It uses the best possible APIs on different platforms which brings resolution up to nanoseconds. It also makes possible to implement a custom stopwatch using low level ticks delivered by the underlying APIs. As of PHP 7.3.0 the related function hrtime is part of the core. &reference.hrtime.setup; &reference.hrtime.examples; &reference.hrtime.hrtime.performancecounter; &reference.hrtime.hrtime.stopwatch; &reference.hrtime.hrtime.unit;