Introduction

What is it?

php-opcua/opcua-client is a pure PHP client for OPC UA. It speaks the binary protocol over TCP, handles secure channels, sessions, and cryptography — no C/C++ extensions required. Just PHP and ext-openssl.

Requirements

• PHP >= 8.2
• ext-openssl

Installation

composer require php-opcua/opcua-client

Quick Start

use PhpOpcua\Client\ClientBuilder;
use PhpOpcua\Client\Types\NodeId;
use PhpOpcua\Client\Types\StatusCode;

$client = ClientBuilder::create()
    ->connect('opc.tcp://localhost:4840');

// Read a value
$dataValue = $client->read(NodeId::numeric(0, 2259));

if (StatusCode::isGood($dataValue->statusCode)) {
    echo "Server status: " . $dataValue->getValue();
}

// Browse the Objects folder
$references = $client->browse(NodeId::numeric(0, 85));

foreach ($references as $ref) {
    echo $ref->displayName . "\n";
}

$client->disconnect();

Features

Protocol & Transport

• Full OPC UA binary encoding/decoding over TCP
• Configurable timeouts for connection and I/O

Browsing & Navigation

• Browse the server address space with automatic continuation
• Recursive browsing with cycle detection
• Path resolution via TranslateBrowsePathsToNodeIds — turn "/Objects/MyPLC/Temperature" into a NodeId
• Cache for browse and resolve results — InMemoryCache (default) and FileCache included

Read & Write

• Read and write node attributes, single or multi
• Automatic batching when the server imposes per-request limits
• Human-readable NodeId strings — all methods accept 'i=2259' or 'ns=2;s=MyNode' in addition to NodeId objects

Advanced

• Method calls on the server
• Subscriptions with data change and event monitoring
• History reads (raw, processed, at-time)
• Endpoint discovery
• Pluggable ExtensionObject codecs for custom structures
• Automatic DataType discovery — auto-detect and decode custom structures without writing codecs

Security

• 10 security policies: 6 RSA (None through Aes256Sha256RsaPss) + 4 ECC (EccNistP256, EccNistP384, EccBrainpoolP256r1, EccBrainpoolP384r1)
• 3 security modes (None, Sign, SignAndEncrypt)
• Anonymous, username/password, and X.509 certificate authentication
• PEM and DER certificate support with auto-detection
• Persistent server certificate trust store with configurable validation policies
• TOFU (Trust On First Use) auto-accept for new certificates

Observability

• PSR-3 logging — pass any compatible logger (Monolog, Laravel, etc.) for structured diagnostics
• NullLogger by default — zero overhead when logging is not needed
• PSR-14 events — 47 granular events dispatched at lifecycle points (connection, session, subscription, data change, alarms, read/write, write type detection, browse, cache, retry, trust store)
• NullEventDispatcher by default — zero overhead when events are not needed

Testing

• MockClient for testing — implements OpcUaClientInterface with no TCP connection, register handlers, assert calls

Reliability

• Connection state tracking (Disconnected, Connected, Broken)
• reconnect() for re-establishing dropped connections
• Auto-retry on connection failures

Architecture

Client (main entry point)
  |
  +-- Transport/TcpTransport        TCP socket communication
  +-- Protocol/*Service              OPC UA service encoding/decoding
  +-- Encoding/BinaryEncoder         Binary serialization
  +-- Encoding/BinaryDecoder         Binary deserialization
  +-- Security/SecureChannel         Message-level security
  +-- Security/MessageSecurity       Crypto operations
  +-- Security/CertificateManager    Certificate handling
  +-- Types/*                        OPC UA data types
  +-- Exception/*                    Error hierarchy