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MonotonicClock — monotonic clock

Purpose

Readings never go backwards even when the system clock is set back (NTP correction, manual change): the delta comes from hrtime().

What for and how to use

Interval measurement, rate limiting, timeouts in long-lived processes (daemons, queue workers).

Example

$clock = new MonotonicClock('UTC');
$start = $clock->microtime();
// ... the system clock is moved backwards ...
$elapsed = $clock->microtime() - $start;   // still >= 0

Anti-patterns

Not for wall-clock time: readings diverge from the real clock after it is adjusted.

Lifecycle

stateDiagram-v2
    [*] --> Anchored: new MonotonicClock()
    Anchored --> Reading: now() = anchor + hrtime delta
    Reading --> Reading: monotonic growth
    note right of Reading: system clock jumps\ndo not affect readings

Feature comparison with competitors

Aspect	🏆 CloudCastle	symfony	carbon	lcobucci	beste	ergebnis
Resilience to system clock rollback	✅	✅	❌	❌	❌	❌
Nanosecond base (`hrtime`)	✅	✅	❌	❌	❌	❌
Full clock contract (timestamp/microtime)	✅	❌	❌	❌	❌	❌
Arbitrary output timezone	✅	✅	❌	❌	❌	❌
Real `sleep()`/`sleepUntil()` resuming after a signal	✅	✅	❌	❌	❌	❌
Total	🏆 5	4	0	0	0	0

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