Overview

php-opcua/opcua-client is a client implementation of OPC UA, written entirely in PHP. It connects to an OPC UA server over opc.tcp://, opens a secure channel and a session, then issues service calls — read, write, browse, subscribe, history, method call, node management — and returns typed PHP objects.

The project targets industrial automation use cases where a PHP backend needs to talk to a PLC, a SCADA server, or any device exposing OPC UA. It is synchronous, single-threaded, and has no runtime dependency outside ext-openssl.

When to use it

Reach for this library when you want to:

• Read or write PLC tags from a Laravel / Symfony / plain-PHP application.
• Build an integration layer that browses an industrial address space and exposes parts of it as an API, queue producer, or webhook.
• Subscribe to live data changes or alarm events from a long-running worker.
• Implement bespoke supervisory tools without leaving PHP.

The library is not an OPC UA server, and it is not asynchronous — each call blocks the calling process. For session persistence across short-lived requests, pair it with the companion opcua-session-manager daemon.

What is in the box

ClientBuilder       fluent configuration entry point
   │
   └── Client       proxy to 10 self-contained service modules:
          ReadWrite · Browse · Subscription · History ·
          NodeManagement · TranslateBrowsePath ·
          ServerInfo · TypeDiscovery · Aggregate · FileTransfer

SecureChannel       message-level cryptography
Transport           TCP socket I/O
TrustStore          server certificate validation
Cache               browse / resolve / type caching, codec-gated
Event dispatcher    47 PSR-14 events at every lifecycle point

The client speaks 10 security policies — None (no cryptography), five RSA (Basic128Rsa15, Basic256, Basic256Sha256, Aes128Sha256RsaOaep, Aes256Sha256RsaPss), and four ECC (EccNistP256, EccNistP384, EccBrainpoolP256r1, EccBrainpoolP384r1). Authentication covers anonymous, username/password, and X.509 certificate flows.

Reading order

This documentation is organised by reader intent, not by class layout:

• Getting started walks you from composer require to a first read in three pages. Read it once.
• Connection covers endpoint discovery, the session lifecycle, and retry semantics. Come back here when network behaviour is the topic.
• Operations is one page per OPC UA service set. Use it as the recipe shelf for everyday work.
• Security, Types, Observability, Testing are topic-specific deep-dives. Reach for them when the task warrants.
• Extensibility is for readers wiring custom modules, codecs, or IPC layers.
• Reference is the alphabetical surface — every public method, exception, and enum.
• Recipes are short, focused walkthroughs for tasks the code does not auto-explain.

Conventions in these docs

• Code samples are runnable as-is unless they say otherwise.
• // … in a sample means "irrelevant code elided".
• Type names use their unqualified form (NodeId, not PhpOpcua\Client\Types\NodeId) when context disambiguates; otherwise the full namespace is shown.
• Status codes use their canonical OPC UA names (BadServiceUnsupported, Good) — see Reference · Enums for the numeric values.

What this library does not do

• Asynchronous I/O. Every call blocks. For non-blocking integration, put the client behind a worker or behind opcua-session-manager.
• OPC UA Pub/Sub. Out of scope; the opcua-client-ext-pubsub extension is a separate package.
• An OPC UA server. Client-only by design — implementing a conformant server requires an entirely different architecture (address space management, session handling, subscription engine).
• CLI tools. Browse / read / write / trust management from the terminal lives in php-opcua/opcua-cli.