feat(php): Enable FFE tests and add /ffe endpoints

- Add /ffe/start and /ffe/evaluate to PHP parametric server
- Add /ffe.php for end-to-end tests
- Remove missing_feature for PHP FFE tests in manifest

Author: leoromanovsky

manifests/php.yml

@@ -474,8 +474,6 @@ manifest:
   tests/docker_ssi/test_docker_ssi.py::TestDockerSSIFeatures::test_instrumentation_source_ssi:
     - declaration: missing_feature (Not implemented yet)
       component_version: <1.12.0
-  tests/ffe/test_dynamic_evaluation.py: missing_feature
-  tests/ffe/test_exposures.py: missing_feature
   tests/integrations/crossed_integrations/test_kafka.py::Test_Kafka: missing_feature
   tests/integrations/crossed_integrations/test_kinesis.py::Test_Kinesis_PROPAGATION_VIA_MESSAGE_ATTRIBUTES: missing_feature
   tests/integrations/crossed_integrations/test_rabbitmq.py::Test_RabbitMQ_Trace_Context_Propagation: missing_feature
@@ -532,7 +530,6 @@ manifest:
   tests/parametric/test_dynamic_configuration.py::TestDynamicConfigV1_EmptyServiceTargets: v1.4.0
   tests/parametric/test_dynamic_configuration.py::TestDynamicConfigV1_ServiceTargets: missing_feature
   tests/parametric/test_dynamic_configuration.py::TestDynamicConfigV2: missing_feature
-  tests/parametric/test_ffe/test_dynamic_evaluation.py::Test_Feature_Flag_Dynamic_Evaluation: missing_feature
   tests/parametric/test_headers_b3.py::Test_Headers_B3::test_headers_b3_migrated_extract_invalid: missing_feature (Need to remove b3=b3multi alias)
   tests/parametric/test_headers_b3.py::Test_Headers_B3::test_headers_b3_migrated_extract_valid: missing_feature (Need to remove b3=b3multi alias)
   tests/parametric/test_headers_b3.py::Test_Headers_B3::test_headers_b3_migrated_inject_valid: missing_feature (Need to remove b3=b3multi alias)

utils/build/docker/php/common/ffe.php

@@ -0,0 +1,31 @@
+<?php
+
+header('Content-Type: application/json');
+
+$input = json_decode(file_get_contents('php://input'), true);
+
+if (!is_array($input)) {
+    http_response_code(400);
+    echo json_encode(['error' => 'Invalid JSON body']);
+    exit;
+}
+
+$flag = isset($input['flag']) ? $input['flag'] : null;
+$variationType = isset($input['variationType']) ? $input['variationType'] : null;
+$defaultValue = isset($input['defaultValue']) ? $input['defaultValue'] : null;
+$targetingKey = array_key_exists('targetingKey', $input) ? $input['targetingKey'] : '';
+$attributes = isset($input['attributes']) ? $input['attributes'] : [];
+
+try {
+    $provider = \DDTrace\FeatureFlags\Provider::getInstance();
+    $provider->start();
+
+    $result = $provider->evaluate($flag, $variationType, $defaultValue, $targetingKey, $attributes);
+
+    // Flush exposure events immediately for system test observability
+    $provider->flush();
+
+    echo json_encode($result);
+} catch (\Throwable $e) {
+    echo json_encode(['value' => $defaultValue, 'reason' => 'ERROR', 'error' => $e->getMessage()]);
+}

utils/build/docker/php/parametric/server.php

@@ -546,6 +546,41 @@ function remappedSpanKind($spanKind) {
     return jsonResponse([]);
 }));
 
+// FFE (Feature Flags & Experimentation) endpoints
+$ffeProvider = null;
+
+$router->addRoute('POST', '/ffe/start', new ClosureRequestHandler(function (Request $req) use (&$ffeProvider) {
+    try {
+        if ($ffeProvider === null) {
+            $ffeProvider = \DDTrace\FeatureFlags\Provider::getInstance();
+        }
+        $ffeProvider->start();
+        return jsonResponse([]);
+    } catch (\Throwable $e) {
+        return new Response(status: 500, body: json_encode(['error' => $e->getMessage()]));
+    }
+}));
+
+$router->addRoute('POST', '/ffe/evaluate', new ClosureRequestHandler(function (Request $req) use (&$ffeProvider) {
+    try {
+        if ($ffeProvider === null) {
+            $ffeProvider = \DDTrace\FeatureFlags\Provider::getInstance();
+            $ffeProvider->start();
+        }
+
+        $flag = arg($req, 'flag');
+        $variationType = arg($req, 'variationType');
+        $defaultValue = arg($req, 'defaultValue');
+        $targetingKey = arg($req, 'targetingKey');
+        $attributes = arg($req, 'attributes') ?? [];
+
+        $result = $ffeProvider->evaluate($flag, $variationType, $defaultValue, $targetingKey, $attributes);
+        return jsonResponse($result);
+    } catch (\Throwable $e) {
+        return new Response(status: 500, body: json_encode(['error' => $e->getMessage()]));
+    }
+}));
+
 $middleware = new class implements Middleware {
     public function handleRequest(Request $request, RequestHandler $next): Response {
         $response = $next->handleRequest($request);