Docs · Observability

Event reference

The full event catalogue — 56 classes grouped by lifecycle. Each event carries a $client reference plus a handful of typed fields.

The library dispatches 58 event classes. Every event extends a common shape with a $client property; the per-event fields below are the additions on top of that.

All event classes live in PhpOpcua\Client\Event\.

Connection lifecycle (6)

Event	Fires when	Key fields
`ClientConnecting`	`connect()` starts	`endpoint`
`ClientConnected`	Session is activated	`endpoint`, `sessionId`
`ClientDisconnecting`	`disconnect()` starts	—
`ClientDisconnected`	Disconnect completed (clean or broken)	— (only `$client`)
`ClientReconnecting`	`reconnect()` starts	`endpoint`
`ConnectionFailed`	`connect()` raised	`endpoint`, `exception`

Secure channel (3)

Event	Fires when	Key fields
`SecureChannelOpened`	OPN exchange completed	`channelId`, `securityPolicy` (enum), `securityMode`
`SecureChannelClosed`	CLO sent or socket dropped	`channelId`
`SecureChannelRenewed`	Security token renewed (75% of its lifetime)	`channelId`, `tokenId`, `revisedLifetime`

Session (4)

Event	Fires when	Key fields
`SessionCreated`	After CreateSession	`sessionId`, `sessionName`
`SessionActivated`	After ActivateSession	`sessionId`
`SessionClosed`	After CloseSession	`sessionId`
`SessionReactivated`	An existing session was reactivated on a new secure channel	`endpointUrl`

Read / Write (3)

Event	Fires when	Key fields
`NodeValueRead`	`read()` succeeded	`nodeId`, `attributeId`, `dataValue`
`NodeValueWritten`	`write()` returned Good	`nodeId`, `value`, `type`
`NodeValueWriteFailed`	`write()` returned non-Good	`nodeId`, `value`, `type`, `statusCode`

Write type detection (2)

Event	Fires when	Key fields
`WriteTypeDetecting`	Auto-detection started for a node	`nodeId`
`WriteTypeDetected`	Auto-detection produced a `BuiltinType`	`nodeId`, `detectedType`, `fromCache`

Browse (1)

Event	Fires when	Key fields
`NodeBrowsed`	`browse()` succeeded	`nodeId`, `direction`, `referenceCount`

Subscriptions (4)

Event	Fires when	Key fields
`SubscriptionCreated`	`createSubscription()` succeeded	`subscriptionId`, `revisedPublishingInterval`
`SubscriptionDeleted`	`deleteSubscription()` succeeded	`subscriptionId`
`SubscriptionKeepAlive`	`publish()` got an empty response	`subscriptionId`, `sequenceNumber`
`SubscriptionTransferred`	`transferSubscriptions()` returned, once per subscription	`subscriptionId`, `statusCode`

Monitored items (3)

Event	Fires when	Key fields
`MonitoredItemCreated`	`createMonitoredItems()` / `createEventMonitoredItem()` returned, once per item	`subscriptionId`, `monitoredItemId`, `nodeId`, `statusCode`
`MonitoredItemModified`	`modifyMonitoredItems()` returned, once per item	`subscriptionId`, `monitoredItemId`, `statusCode`
`MonitoredItemDeleted`	`deleteMonitoredItems()` returned, once per item	`subscriptionId`, `monitoredItemId`, `statusCode`

The monitored item events fire for every result, including rejected items: check statusCode.

Publish (3)

Event	Fires when	Key fields
`DataChangeReceived`	`publish()` / `republish()` delivered a data-change notification	`subscriptionId`, `sequenceNumber`, `clientHandle`, `dataValue`, `republished`
`EventNotificationReceived`	`publish()` / `republish()` delivered an event notification	`subscriptionId`, `sequenceNumber`, `clientHandle`, `eventFields`, `republished`
`PublishResponseReceived`	Any `publish()` response (including keep-alives)	`subscriptionId`, `sequenceNumber`, `notificationCount`, `moreNotifications`

republished is true when the notification came from republish(). A retransmission can repeat a notification publish() already delivered, so check it when a value must not be processed twice. PublishResponseReceived and SubscriptionKeepAlive are dispatched by publish() only.

Triggering (1)

Event	Fires when	Key fields
`TriggeringConfigured`	`setTriggering()` returned	`subscriptionId`, `triggeringItemId`, `addResults`, `removeResults`

Alarms (9)

These are deduced from event notification payloads, in addition to EventNotificationReceived. The deduction reads the fields by position, so it assumes the default select clauses of createEventMonitoredItem() (EventId, EventType, SourceName, Time, Message, Severity) followed by any state fields. Every alarm event also carries subscriptionId, clientHandle and republished.

Event	Fires when	Key fields
`AlarmEventReceived`	The event has a `Severity` or an `EventType`	`eventFields`, `severity`, `sourceName`, `message`, `eventType`, `time`
`AlarmSeverityChanged`	An alarm-shaped event carries a `Severity` (every time, not only on change)	`sourceName`, `severity`
`LimitAlarmExceeded`	`EventType` is a LimitAlarmType variant	`sourceName`, `limitState`, `severity`
`OffNormalAlarmTriggered`	`EventType` is an OffNormalAlarmType variant	`sourceName`, `severity`
`AlarmActivated`	The first state field is `true`, or a string starting with `Active`	`sourceName`, `severity`, `message`
`AlarmDeactivated`	The first state field is `false`, or a string starting with `Inactive`	`sourceName`, `message`
`AlarmAcknowledged`	The first state field is a string containing `Acknowledged` or `Acked`	`sourceName`
`AlarmConfirmed`	The first state field is a string containing `Confirmed`	`sourceName`
`AlarmShelved`	The first state field is a string containing `Shelved`	`sourceName`

Type discovery (1)

Event	Fires when	Key fields
`DataTypesDiscovered`	`discoverDataTypes()` completed	`namespaceIndex`, `count`

History updates (4)

Dispatched after each HistoryUpdate call returns.

Event	Fires when	Key fields
`HistoryDataUpdated`	`historyInsertData()` / `historyReplaceData()` / `historyUpdateData()` returned	`nodeId`, `operation` (`PerformUpdateType`), `valueCount`, `operationResults` (`int[]`)
`HistoryDataDeleted`	`historyDeleteRawModified()` (`kind: 'rawModified'`) or `historyDeleteAtTime()` (`kind: 'atTime'`) returned	`nodeId`, `kind` (`string`), `statusCode` (`int`), `operationResults` (`int[]`, populated only for `atTime`)
`HistoryEventUpdated`	`historyInsertEvent()` / `historyReplaceEvent()` / `historyUpdateEvent()` returned	`nodeId`, `operation` (`PerformUpdateType`), `eventCount`, `operationResults` (`int[]`)
`HistoryEventDeleted`	`historyDeleteEvent()` returned	`nodeId`, `eventCount`, `operationResults` (`int[]`)

PerformUpdateType is an int-backed enum (Insert=1, Replace=2, Update=3, Remove=4) — see Operations · History writes.

Aggregates (1)

Dispatched after the client-side aggregator finishes a windowed computation.

Event	Fires when	Key fields
`AggregateComputed`	`aggregate()` or `historyAggregate()` returned	`function` (`AggregateFunction`), `rawInputCount`, `intervalCount`, `nodeId` (`?NodeId`, null for in-memory)

See Operations · Client-side aggregates.

File Transfer (4)

Dispatched after each File Transfer call returns.

Event	Fires when	Key fields
`FileOpened`	`openFile()` returned	`fileNodeId`, `fileHandle`, `mode` (Byte bit-field per Part 5 §C.2.1)
`FileClosed`	`closeFile()` returned	`fileNodeId`, `fileHandle`
`FileBytesRead`	`readFile()` returned	`fileNodeId`, `fileHandle`, `bytesRead`, `requestedLength` (may differ on EOF)
`FileBytesWritten`	`writeFile()` returned	`fileNodeId`, `fileHandle`, `bytesWritten`

getFilePosition() and setFilePosition() do not dispatch events — they're considered low-noise diagnostics. See Operations · File Transfer.

Cache (2)

Event	Fires when	Key fields
`CacheHit`	A cached value was returned	`key`, `operation`, `nodeId`
`CacheMiss`	A miss triggered a server round-trip	`key`, `operation`, `nodeId`

Retry (2)

Event	Fires when	Key fields
`RetryAttempt`	A retry is about to run	`operation`, `attempt`, `exception`
`RetryExhausted`	The retry budget is exhausted and the call fails	`operation`, `attempts`, `exception`

Trust store (5)

Event	Fires when	Key fields
`ServerCertificateTrusted`	Cert was already in store, accepted	`fingerprint`
`ServerCertificateAutoAccepted`	TOFU recorded a new cert	`fingerprint`
`ServerCertificateRejected`	Cert was rejected (validation failed)	`fingerprint`, `reason`
`ServerCertificateManuallyTrusted`	`trustCertificate()` was called	`fingerprint`
`ServerCertificateRemoved`	`untrustCertificate()` was called	`fingerprint`

Putting them in context

You want	Listen for
"Tell me when the connection is up"	`ClientConnected`
"Tell me when it breaks"	`ConnectionFailed` (raised exception); `ClientDisconnected` covers both clean and broken
"Count reads"	`NodeValueRead`
"Count failed writes"	`NodeValueWriteFailed`
"Page on critical alarms"	`AlarmActivated` filtered by `severity`
"Measure cache effectiveness"	`CacheHit` and `CacheMiss`
"Track retry behaviour"	`RetryAttempt`, `RetryExhausted`
"Audit certificate trust decisions"	The five trust-store events

For wiring patterns, see Events. For events you want to trigger programmatically (in tests), see Testing · MockClient.

Last updated · 2026-09-17

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