Docs · Types

Types overview

The type system is small on the surface — Variant, DataValue, NodeId, ExtensionObject — and everything else is a refinement. Internalise these four and the rest follows.

OPC UA has a generous type system; this library exposes it through a small set of PHP value objects, all read-only and immutable.

The four pillars

Type	Role
`NodeId`	Address-space identity
`Variant`	Typed value container — wraps a PHP value with its `BuiltinType`
`DataValue`	A `Variant` plus a status code and two timestamps
`ExtensionObject`	A typed structure (raw bytes or decoded)

Every value crossing the OPC UA wire is one of these. Read returns DataValue. Write takes a value the library wraps in a Variant. Browse returns ReferenceDescription, which is built from NodeId, QualifiedName, and LocalizedText. Methods return Variant[] for their outputs.

Value object discipline

Every type in PhpOpcua\Client\Types\ is:

A final PHP class with public readonly properties.
Constructed once, never mutated. To "change" a field you build a new instance.
Serialisable through Wire\WireSerializable for IPC use.

This means you can pass these objects around freely — they cannot drift under you, and equality is structural.

php property access, not getters

$dv = $client->read('i=2261');

echo $dv->statusCode;            // int
echo $dv->sourceTimestamp?->format('c');
echo $dv->getValue();            // the unwrapped PHP value

// Pre-v3 getters still exist (deprecated):
$dv->getValue();                 // ok
$dv->getStatusCode();            // ok but deprecated — use $dv->statusCode

Property access is the idiomatic style. The deprecated getX() helpers exist for migrations from older versions and will be removed in v5.

Enum types

Several configuration surfaces are PHP 8.1 backed enums:

Enum	Cases
`BuiltinType`	25 cases — `Boolean`, `Int32`, `Double`, … See Built-in types.
`NodeClass`	8 cases — `Object`, `Variable`, `Method`, …
`BrowseDirection`	3 cases — `Forward`, `Inverse`, `Both`
`ConnectionState`	3 cases — `Disconnected`, `Connected`, `Broken`
`SecurityPolicy`	10 cases — see Security · Policies
`SecurityMode`	3 cases — `None`, `Sign`, `SignAndEncrypt`
`TrustPolicy`	3 cases — `Fingerprint`, `FingerprintAndExpiry`, `Full`

All are backed enums; their value corresponds to the OPC UA-spec integer or URI. BuiltinType::from(11) returns BuiltinType::Double.

Module-scoped DTOs

Service methods return DTOs that live in the relevant module namespace, not in Types\. These are still read-only public-property classes, but they document a specific service's result shape:

DTO	Returned by
`Module\Browse\BrowseResultSet`	`browseWithContinuation()`
`Module\TranslateBrowsePath\BrowsePathResult`	`translateBrowsePaths()`
`Module\TranslateBrowsePath\BrowsePathTarget`	inside `BrowsePathResult`
`Module\ReadWrite\CallResult`	`call()`
`Module\Subscription\SubscriptionResult`	`createSubscription()`
`Module\Subscription\MonitoredItemResult`	`createMonitoredItems()`
`Module\Subscription\MonitoredItemModifyResult`	`modifyMonitoredItems()`
`Module\Subscription\SetTriggeringResult`	`setTriggering()`
`Module\Subscription\PublishResult`	`publish()`
`Module\Subscription\TransferResult`	`transferSubscriptions()`
`Module\NodeManagement\AddNodesResult`	`addNodes()`
`Module\ServerInfo\BuildInfo`	`getServerBuildInfo()`

These DTOs are not deep — most are status code + a payload tuple. The field-by-field details are in the relevant operations pages.

Status codes

Status codes are 32-bit OPC UA integers, not enums. They are passed as int and tested with helpers on the StatusCode class:

php status code helpers

use PhpOpcua\Client\Types\StatusCode;

if (StatusCode::isGood($dv->statusCode)) { … }
if (StatusCode::isBad($dv->statusCode))  { … }
if (StatusCode::isUncertain($dv->statusCode)) { … }

echo StatusCode::getName($dv->statusCode);   // "Good", "BadNodeIdUnknown", …

The full list of named codes is in Reference · Enums.