Performance

Near-zero overhead when the SDK is inactive — every component short-circuits via isEnabled(). When tracing is on, almost all cost is in span export, not instrumentation. PHP-FPM has no background thread, so BatchSpanProcessor flushes during request shutdown.

Use http/json unless you have ext-protobuf installed. PHP's native json_encode() is faster than the pure-PHP protobuf encoder, which adds significant CPU overhead under load. Switch to http/protobuf only with the C extension installed.

For high-traffic apps:

• Run a local OTel Collector at localhost:4318 (sub-ms latency) and let it forward asynchronously.
• Enable head sampling: OTEL_TRACES_SAMPLER=parentbased_traceidratio + OTEL_TRACES_SAMPLER_ARG=0.1.
• Use traces.excluded_paths / traces.cache.excluded_pools to drop noisy spans.