feat(ffe): wire remote config lifecycle

[leoromanovsky]

Motivation

Continue the OpenFeature PHP compatibility stack by wiring the native evaluator to Remote Config. This PR follows the libdatadog import pattern from #3630 so the tracer subscribes to FFE Remote Config payloads and hands them to datadog-ffe instead of parsing or evaluating rules in PHP.

Reference design doc: https://docs.google.com/document/d/1NvMfTpZWLBlFmEFNjdnlMyeVpy5l7KD8qujGFco6w2w/edit?tab=t.0

Stack base: #3903

Changes

• Enables the ffe feature on datadog-remote-config.
• Replaces positional ddog_init_remote_config bools with a named C-ABI flags struct.
• Adds DD_EXPERIMENTAL_FLAGGING_PROVIDER_ENABLED, defaulting to false.
• Subscribes to FFE_FLAGS plus FfeFlagConfigurationRules only when the experimental provider is enabled.
• Stores and clears datadog_ffe::rules_based::Configuration on FFE Remote Config add/remove events.
• Adds a dev-env PHPT for FFE Remote Config add/evaluate/remove lifecycle.

Decisions

• Keep the Remote Config subscription behind DD_EXPERIMENTAL_FLAGGING_PROVIDER_ENABLED=false so partially landed stack work does not surprise users.
• Keep UFC parsing and rule evaluation owned by libdatadog/datadog-ffe; PHP only bridges config lifecycle and evaluation calls.
• Mark the lifecycle PHPT as dev-env-only because it depends on request-replayer, matching existing Remote Config tests.

Validation

• git diff --check
• php -n -l tests/ext/ffe/remote_config_lifecycle.phpt
• RUSTC_BOOTSTRAP=1 cargo check -p ddtrace-php
• EXTRA_CFLAGS="-I$(brew --prefix pcre2)/include" EXTRA_LDFLAGS="-L$(brew --prefix pcre2)/lib" make -j"$(sysctl -n hw.ncpu)"
• php -n -d extension=tmp/build_extension/modules/ddtrace.so -m | rg -i '^ddtrace$'
• make test_c TESTS=tests/ext/ffe/native_bridge_evaluate.phpt
• make test_c TESTS=tests/ext/ffe/remote_config_lifecycle.phpt skipped locally because request-replayer is not available outside the Datadog dev env.

[datadog-datadog-prod-us1-2]

 

✨ Fix all issues with BitsAI

⚠️ Warnings

🚦 17 Pipeline jobs failed

DataDog/apm-reliability/dd-trace-php | API unit tests: [7.0]     

🔧 Fix in code (Fix with Cursor).

1 failed test in ClientTest::testUnavailableRuntimeReturnsDefaultWithProviderNotReadyDetailsAndWarning. Expected string not identical to actual output at tests/api/Unit/FeatureFlags/ClientTest.php:107.

DataDog/apm-reliability/dd-trace-php | API unit tests: [7.1]     

🔧 Fix in code (Fix with Cursor).

1 failed test. Error: Failed asserting that two strings are identical in ClientTest.php:107.

DataDog/apm-reliability/dd-trace-php | API unit tests: [7.2]     

🔧 Fix in code (Fix with Cursor).

1 failed test. Error: Failed asserting that two strings are identical in ClientTest.php:107.

View all 17 failed jobs.

ℹ️ Info

No other issues found (see more)

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 60.74% (+0.04%)

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[pr-commenter]

Benchmarks [ tracer ]

Benchmark execution time: 2026-05-22 02:02:17

Comparing candidate commit cae2759 in PR branch leo.romanovsky/pr-i-remote-config-lifecycle with baseline commit d712d6b in branch leo.romanovsky/pr-h-native-bridge.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 194 metrics, 0 unstable metrics.