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Context Engine PHP SDK

PHP 8.1+ client for the scoped Context Engine API introduced by CE-CONTRACT-TRANSPORT-PARITY-001 (CE PR #144). The canonical application client uses HTTP. An optional Redis request/reply helper remains available.

Installation

Requires PHP 8.1+, ext-curl and ext-json. The Composer package name stays robo-meister/context-engine-api; this change does not create a release tag.

For a local checkout, add this to your application's composer.json:

Then run composer update robo-meister/context-engine-api and load vendor/autoload.php. For direct installation copy all four root PHP files, including ContextEngineException.php and ScopedContextClientInterface.php, then require_once 'ContextEngineClient.php' (and the Redis client if used).

Scoped API

One resolve call sends one request for all supplied keys. The SDK preserves scope order; CE checks each scope's active STATE, active CACHE, then default, before moving to the next scope. It neither expands dependencies nor implements a local resolver. With active, omitted kind reads STATE then CACHE; on unset it removes both kinds. With default, kind is not accepted.

TTL is a positive integer in seconds. null omits TTL; default has no TTL parameter. Version, scopeRef, store, kind, updatedBy, updatedAt, ttlSeconds and expiresAt are returned as supplied by CE. Optional fields stay optional, and unknown metadata fields are preserved. Server timestamps are epoch milliseconds. Version increases for an existing record; it can restart after expiry or deletion. The SDK does not manufacture a version or renew expiry on read.

Results are associative PHP arrays. JSON objects decode to arrays, and JSON integers beyond the platform integer range decode to strings. Use array_key_exists to distinguish an explicit null value from a missing key; false, zero and empty strings remain values. Mutations return acknowledgements, not the new metadata. Read explicitly when an application needs the resulting version or preview.

Authentication and failures

The existing constructor's first four parameters are unchanged. For a gateway using bearer authentication, supply bearerToken instead of apiKey:

HTTPS is required by default. For an explicitly trusted local endpoint use new ContextEngineClient('http://localhost:8080', timeout: 8, enforceHttps: false). Certificate verification stays enabled for HTTPS, and redirects are never followed. The SDK does not exchange OAuth tokens or infer account/subscription permissions. Scope selection and updatedBy are data, not proof of authority: your trusted application/gateway must enforce access. CE PR #144's WebServer does not itself validate these authentication headers.

Scoped failures use invalid_request, transport_error, http_error, invalid_json or invalid_response. HTTP failures preserve status, body and headers, but the default exception message excludes the body and credentials. Existing RuntimeException catches still work; constructor configuration errors remain RuntimeException. There is no automatic retry, fallback transport, or missing-context substitution on a failed request. In particular, CE HTTP writes do not expose mutation idempotency keys: a timeout can leave their outcome unknown.

Compatibility and server limits

getContext, upsertContext, deleteContext and searchContext retain their signatures and legacy /context routes. That facade uses ce:context:* and does not expose canonical scoped records from events. RC must explicitly migrate its context reads to the scoped API; installing this SDK alone does not switch them.

The scoped client targets CE 12683d8051314334cae234968a38accfbf2b5456 (main after PR #144). Current server limitations are made explicit:

• Scope type/ID must match [A-Za-z0-9_-][A-Za-z0-9_.-]*. This excludes ambiguous delimiters and encoded path characters that the current server double-decodes.
• Keys are non-empty strings, without colons, control characters or surrounding whitespace. Scoped writes reject kind, ttl, updatedBy and principal as value keys because this server removes them even from the nested values map.
• Stream projection lowercases scope types and normalizes projected field names; HTTP preserves them. For cross-transport reads use matching lowercase scope types and lowercase ASCII keys with digits, underscores, dots or hyphens. The SDK never silently renames data.
• Event updatedBy currently derives from principal.id, then actor/source; the server does not map principal.principalId here.

These constraints need server-side follow-up before the SDK can relax them. This PR does not claim full RC/event-mapper interoperability or fix server lifecycle.

Optional Redis request/reply

This is the existing Pub/Sub control bridge, not the durable event stream. It requires a running CE RedisRequestListener and a caller-supplied Redis client configured without transparent serialization. sendRequest(..., true) returns the bridge envelope (status, JSON-string body, request_id), not the scoped HTTP client's result. HTTP status errors inside that envelope must be checked.

The control bridge is for trusted internal Redis clients. The current server bridge does not forward SDK HTTP authentication headers. Redis connection/auth/ACL configuration remains owned by the application and infrastructure.

waitForResponse: false returns the request ID after publish; it does not prove that a listener received the request or that context was updated. Pub/Sub does not queue messages for disconnected listeners. No automatic retry is performed. Both false (phpredis) and null (other clients) mean a reply key is still absent.

Defaults remain context_engine:requests, context_engine:response: and context_engine:greeting. The helper rejects CE stream/state key namespaces (including ce:events) for its request/reply/greeting configuration. If the stream has a custom name, pass that name as eventsStreamKey too. There is no SET operation on the event stream, no key deletion to repair a wrong type, and no implicit direct read of CE state keys.

For applications using the optional PHP handleRequests worker, a separate responseWriter Redis connection is now required. Subscribed connections cannot safely write responses. The worker writes JSON via SETEX with responseTtlSeconds (default 300), and only accepts reply keys with its configured prefix plus the SDK's 16-character hex request ID. Other request-ID formats need an explicit application adapter. Validate/authenticate business payloads in your handler. Existing calls to sendRequest do not need a response writer.

Verification

Runs legacy constructor checks, local HTTP contract tests, and Redis helper tests. The HTTP fixture starts on a random loopback port; normal tests need neither a CE server nor a Redis extension/server. They cover request count and scope order, PATCH payloads, metadata, typed values, errors, no retry/redirect, and reserved keys.

For a disposable local CE + Redis instance matching the server commit above, with its stream consumer and request listener enabled, additionally run:

This requires ext-redis and creates randomized test scopes, stream entries, checkpoints and replay markers. Run only against a disposable local instance. It checks scoped CRUD, resolver precedence, expiry, metadata, bridge PATCH and HTTP parity, event projection visible via /resolve, and replay preserving version/TTL. It does not flush Redis. Stream history/markers remain for disposal with the test instance.