Encodings
Three Part 6 §7.4 encodings (Binary, JSON, XML-SOAP) share one HTTPS transport orchestrator. Per-implementation status lives under /implementations.
OPC UA Part 6 §7.4 defines three encodings that ride on the same HTTPS transport. The transport mechanics (one POST per call, TLS as the secure channel) are identical; the encodings differ only in how the service request and response bodies are serialised.
A fourth — and entirely separate — mapping, the legacy SOAP/HTTP with WS-SecureConversation from Part 6 §7.3 + §6.6, is not a §7.4 encoding: it has its own channel lifecycle and would need a different transport class. It is documented for completeness alongside the others.
| Encoding | Spec | Strategy class | Status (link) |
|---|---|---|---|
| Binary | §7.4.4 | BinaryHttpsEncoding |
Shipped |
| JSON | §7.4.5 | JsonHttpsEncoding |
Foundation shipped |
| XML (SOAP body) | §7.4.3 | XmlSoapHttpsEncoding (planned) |
Roadmap |
| Legacy SOAP/HTTP + WS-SC | §7.3 + §6.6 | WsSoapTransport (planned, separate transport) |
Roadmap |
How the pluggability works
The strategy contract is five methods on {@see PhpOpcua\Client\ExtTransportHttps\Encoding\HttpsEncodingStrategy} — contentType(), acceptHeader(), encodeRequest(), decodeResponse(), fakeAcknowledge(). The HttpsTransport orchestrator delegates everything encoding-specific to the strategy and stays agnostic, so a future strategy (JSON, XML) drops in without touching the transport.
Picking an encoding
Real-world: Binary is the default on every modern OPC UA stack (UA-.NETStandard, open62541, Unified Automation, Prosys, Softing, Kepware). Almost every server advertising "HTTPS" support means HTTPS Binary in practice. JSON appears primarily in PubSub (over MQTT, not HTTPS); XML is essentially absent from new deployments.
If you control the endpoint URL but not the server: pick BinaryHttpsEncoding. If the server advertises a JSON HTTPS endpoint specifically, see the JSON status page for what's usable today versus what's roadmap.
Per-encoding deep dives
For "what works today, what's missing, why" on each of the four mappings, see the dedicated implementation status pages. This page is the conceptual hub; that section is the operational ground truth.