# PHP SDK

The **PHP SDK** provides programmatic access to EventSourcingDB **from PHP applications**. It offers a convenient interface for **writing**, **reading**, and **observing events** without having to interact with the HTTP API directly.

> **Official SDK**
>
> This SDK is **officially developed** and maintained by **[the native web GmbH](https://www.thenativeweb.io)**, the **creators of EventSourcingDB**. It is **aligned with the latest platform features** and **receives regular updates**.

## Installation

To **install the SDK**, run:

```shell
composer require thenativeweb/eventsourcingdb
```

You can also find this SDK on **[Packagist](https://packagist.org/packages/thenativeweb/eventsourcingdb)**.

## Capabilities

This SDK intentionally focuses on **application-level use cases**. It provides **core functionality** for **writing**, **reading**, and **observing events**, and deliberately **excludes operational concerns** such as backup, restore, or health monitoring.

For a detailed explanation of the specific requirements behind each capability, see the **[Compliance Criteria](/docs/eventsourcingdb/sdks/compliance-criteria)**.

> **Compatibility**
>
> PHP SDK 1.1 runs with **EventSourcingDB 1.0** and later.

> **Essentials**
>
> <span style="color:lime;">✓</span> Initialize the Client<br />
> <span style="color:lime;">✓</span> Ping the Server<br />
> <span style="color:lime;">✓</span> Verify API Token

> **Writing Events**
>
> <span style="color:lime;">✓</span> Write Single Events<br />
> <span style="color:lime;">✓</span> Write Multiple Events<br />
> <span style="color:lime;">✓</span> Use `isSubjectPristine`<br />
> <span style="color:lime;">✓</span> Use `isSubjectOnEventId`<br />
> *(Requires EventSourcingDB 1.1)* <span style="color:lime;">✓</span> Use `isEventQlQueryTrue`<br />
> <span style="color:lime;">✓</span> Include OpenTelemetry Trace Context

> **Reading Events**
>
> <span style="color:lime;">✓</span> Read Events by Subject<br />
> <span style="color:lime;">✓</span> Read Recursively<br />
> <span style="color:lime;">✓</span> Read Chronological and Anti-Chronological<br />
> <span style="color:lime;">✓</span> Use Boundaries<br />
> <span style="color:lime;">✓</span> Use `fromLatestEvent`

> **Using EventQL**
>
> <span style="color:lime;">✓</span> Execute EventQL Queries

> **Observing Events**
>
> <span style="color:lime;">✓</span> Observe Events By Subject<br />
> <span style="color:lime;">✓</span> Observe Recursively<br />
> <span style="color:lime;">✓</span> Use Boundaries<br />
> <span style="color:lime;">✓</span> Use `fromLatestEvent`

> **Metadata and Discovery**
>
> <span style="color:lime;">✓</span> Register Event Schemas<br />
> <span style="color:lime;">✓</span> List Subjects<br />
> <span style="color:lime;">✓</span> List Event Types<br />
> *(Requires EventSourcingDB 1.1)* <span style="color:lime;">✓</span> List a Specific Event Type<br />
> *(Added in 1.1)* <span style="color:lime;">✓</span> Verify Event Hashes<br />
> *(Added in 1.1; Requires EventSourcingDB 1.1)* <span style="color:lime;">✓</span> Verify Event Signatures

> **Testcontainers Support**
>
> <span style="color:lime;">✓</span> Start and Stop EventSourcingDB in Tests<br />
> <span style="color:lime;">✓</span> Use Custom Configuration (e.g., API Token, Port, …)

## Getting Started

Import the `Client` class and create an instance by providing the URL of your EventSourcingDB instance and the API token to use:

```php
require __DIR__ . '/vendor/autoload.php';

use Thenativeweb\Eventsourcingdb\Client;

$client = new Client('http://localhost:3000', 'secret');
```

Then call the `ping` function to check whether the instance is reachable. If it is not, the function will throw an exception:

```php
$client->ping();
```

*Note that `ping` does not require authentication, so the call may succeed even if the API token is invalid.*

If you want to verify the API token, call `verifyApiToken`. If the token is invalid, the function will throw an exception:

```php
$client->verifyApiToken();
```

## Writing Events

Call the `writeEvents` function and hand over an array with one or more events. You do not have to provide all event fields – some are automatically added by the server.

Specify `source`, `subject`, `type`, and `data` according to the [CloudEvents](/docs/eventsourcingdb/cloud-events) format.

The function returns the written events, including the fields added by the server:

```php
use Thenativeweb\Eventsourcingdb\EventCandidate;

$writtenEvents = $client->writeEvents([
  new EventCandidate(
    'https://library.eventsourcingdb.io',
    '/books/42',
    'io.eventsourcingdb.library.book-acquired',
    [
      'title' => '2001 – A Space Odyssey',
      'author' => 'Arthur C. Clarke',
      'isbn' => '978-0756906788',
    ],
  ),
]);
```

### Using the `isSubjectPristine` precondition

If you only want to write events in case a subject (such as `/books/42`) does not yet have any events, import the `IsSubjectPristine` class, use it to create a precondition, and pass it in an array as the second argument:

```php
use Thenativeweb\Eventsourcingdb\IsSubjectPristine;

$writtenEvents = $client->writeEvents([
  // events
], [
  new IsSubjectPristine('/books/42'),
]);
```

### Using the `isSubjectOnEventId` precondition

If you only want to write events in case the last event of a subject (such as `/books/42`) has a specific ID (e.g., `0`), import the `IsSubjectOnEventId` class, use it to create a precondition, and pass it in an array as the second argument:

```php
use Thenativeweb\Eventsourcingdb\IsSubjectOnEventId;

$writtenEvents = $client->writeEvents([
  // events
], [
  new IsSubjectOnEventId('/books/42', '0'),
]);
```

*Note that according to the CloudEvents standard, event IDs must be of type string.*

### Using the `isEventQlQueryTrue` precondition *(Requires EventSourcingDB 1.1)*

If you want to write events depending on an EventQL query, use the `IsEventQlQueryTrue` function to create a precondition:

```php
use Thenativeweb\Eventsourcingdb\IsEventQlQueryTrue;

$writtenEvents = $client->writeEvents([
  // events
], [
  new IsEventQlQueryTrue("FROM e IN events WHERE e.type == 'io.eventsourcingdb.library.book-borrowed' PROJECT INTO COUNT() < 10")
]);
```

*Note that the query must return a single row with a single value, which is interpreted as a boolean.*

## Reading Events

To read all events of a subject, call the `readEvents` function with the subject and an options object. Set the `recursive` option to `false`. This ensures that only events of the given subject are returned, not events of nested subjects.

The function returns an iterator, which you can use in a `foreach` loop:

```php
use Thenativeweb\Eventsourcingdb\ReadEventsOptions;

$events = $client->readEvents(
  '/books/42',
  new ReadEventsOptions(
    recursive: false,
  ),
);

foreach ($events as $event) {
  // ...
}
```

### Reading From Subjects Recursively

If you want to read not only all the events of a subject, but also the events of all nested subjects, set the `recursive` option to `true`:

```php
use Thenativeweb\Eventsourcingdb\ReadEventsOptions;

$events = $client->readEvents(
  '/books/42',
  new ReadEventsOptions(
    recursive: true,
  ),
);

foreach ($events as $event) {
  // ...
}
```

This also allows you to read *all* events ever written. To do so, provide `/` as the subject and set `recursive` to `true`, since all subjects are nested under the root subject.

### Reading in Anti-Chronological Order

By default, events are read in chronological order. To read in anti-chronological order, provide the `order` option and set it to `Order::ANTICHRONOLOGICAL`:

```php
use Thenativeweb\Eventsourcingdb\Order;
use Thenativeweb\Eventsourcingdb\ReadEventsOptions;

$events = $client->readEvents(
  '/books/42',
  new ReadEventsOptions(
    recursive: false,
    order: Order::ANTICHRONOLOGICAL,
  ),
);

foreach ($events as $event) {
  // ...
}
```

*Note that you can also use `Order::CHRONOLOGICAL` to explicitly enforce the default order.*

### Specifying Bounds

Sometimes you do not want to read all events, but only a range of events. For that, you can specify the `lowerBound` and `upperBound` options – either one of them or even both at the same time.

Specify the ID and whether to include or exclude it, for both the lower and upper bound:

```php
use Thenativeweb\Eventsourcingdb\Bound;
use Thenativeweb\Eventsourcingdb\BoundType;
use Thenativeweb\Eventsourcingdb\ReadEventsOptions;

$events = $client->readEvents(
  '/books/42',
  new ReadEventsOptions(
    recursive: false,
    lowerBound: new Bound('100', BoundType::INCLUSIVE),
    upperBound: new Bound('200', BoundType::EXCLUSIVE),
  ),
);

foreach ($events as $event) {
  // ...
}
```

### Starting From the Latest Event of a Given Type

To read starting from the latest event of a given type, provide the `fromLatestEvent` option and specify the subject, the type, and how to proceed if no such event exists.

Possible options are `ReadIfEventIsMissing::READ_NOTHING`, which skips reading entirely, or `ReadIfEventIsMissing::READ_EVERYTHING`, which effectively behaves as if `fromLatestEvent` was not specified:

```php
use Thenativeweb\Eventsourcingdb\ReadEventsOptions;
use Thenativeweb\Eventsourcingdb\ReadFromLatestEvent;
use Thenativeweb\Eventsourcingdb\ReadIfEventIsMissing;

$events = $client->readEvents(
  '/books/42',
  new ReadEventsOptions(
    recursive: false,
    fromLatestEvent: new ReadFromLatestEvent(
      subject: '/books/42',
      type: 'io.eventsourcingdb.library.book-borrowed',
      ifEventIsMissing: ReadIfEventIsMissing::READ_EVERYTHING,
    ),
  ),
);

foreach ($events as $event) {
  // ...
}
```

*Note that `fromLatestEvent` and `lowerBound` can not be provided at the same time.*

## Running EventQL Queries

To run an EventQL query, call the `runEventQlQuery` function and provide the query as a string. The function returns an iterator, which you can use in a `foreach` loop:

```php
$rows = $client->runEventQlQuery(
  'FROM e IN events PROJECT INTO e',
);

foreach ($rows as $row) {
  // ...
}
```

*Note that each row returned by the iterator is an associative array and matches the projection specified in your query.*

## Observing Events

To observe all events of a subject, call the `observeEvents` function with the subject as the first argument and an options object as the second argument. Set the `recursive` option to `false`. This ensures that only events of the given subject are returned, not events of nested subjects.

The function returns an asynchronous iterator, which you can use e.g. inside a `foreach` loop:

```php
use Thenativeweb\Eventsourcingdb\ObserveEventsOptions;

$events = $client->observeEvents(
  '/books/42',
  new ObserveEventsOptions(
    recursive: false,
  ),
);

foreach ($events as $event) {
  // ...
}
```

### Observing From Subjects Recursively

If you want to observe not only all the events of a subject, but also the events of all nested subjects, set the `recursive` option to `true`:

```php
use Thenativeweb\Eventsourcingdb\ObserveEventsOptions;

$events = $client->observeEvents(
  '/books/42',
  new ObserveEventsOptions(
    recursive: true,
  ),
);

foreach ($events as $event) {
  // ...
}
```

This also allows you to observe *all* events ever written. To do so, provide `/` as the subject and set `recursive` to `true`, since all subjects are nested under the root subject.

### Specifying Bounds

Sometimes you do not want to observe all events, but only a range of events. For that, you can specify the `lowerBound` option.

Specify the ID and whether to include or exclude it:

```php
use Thenativeweb\Eventsourcingdb\Bound;
use Thenativeweb\Eventsourcingdb\BoundType;
use Thenativeweb\Eventsourcingdb\ObserveEventsOptions;

$events = $client->observeEvents(
  '/books/42',
  new ObserveEventsOptions(
    recursive: false,
    lowerBound: new Bound('100', BoundType::INCLUSIVE),
  ),
);

foreach ($events as $event) {
  // ...
}
```

### Starting From the Latest Event of a Given Type

To observe starting from the latest event of a given type, provide the `fromLatestEvent` option and specify the subject, the type, and how to proceed if no such event exists.

Possible options are `ObserveIfEventIsMissing::WAIT_FOR_EVENT`, which waits for an event of the given type to happen, or `ObserveIfEventIsMissing::READ_EVERYTHING`, which effectively behaves as if `fromLatestEvent` was not specified:

```php
use Thenativeweb\Eventsourcingdb\ObserveEventsOptions;
use Thenativeweb\Eventsourcingdb\ObserveFromLatestEvent;
use Thenativeweb\Eventsourcingdb\ObserveIfEventIsMissing;

$events = $client->observeEvents(
  '/books/42',
  new ObserveEventsOptions(
    recursive: false,
    fromLatestEvent: new ObserveFromLatestEvent(
      subject: '/books/42',
      type: 'io.eventsourcingdb.library.book-borrowed',
      ifEventIsMissing: ObserveIfEventIsMissing::READ_EVERYTHING,
    ),
  ),
);

foreach ($events as $event) {
  // ...
}
```

*Note that `fromLatestEvent` and `lowerBound` can not be provided at the same time.*

### Aborting Observing

If you need to abort observing use `abortIn` before or within the `foreach` loop. The `abortIn` method expects the abort time in seconds. However, this only works if there is currently an iteration going on:

```php
use Thenativeweb\Eventsourcingdb\ObserveEventsOptions;

$events = $client->observeEvents(
  '/books/42',
  new ObserveEventsOptions(
    recursive: false,
  ),
);

$client->abortIn(0.1);
foreach ($events as $event) {
  // ...
  $client->abortIn(0.1);
}
```

## Registering an Event Schema

To register an event schema, call the `registerEventSchema` function and hand over an event type and the desired schema:

```php
$eventType = 'io.eventsourcingdb.library.book-acquired';
$schema = [
  'type' => 'object',
  'properties' => [
    'title' => ['type' => 'string'],
    'author' => ['type' => 'string'],
    'isbn' => ['type' => 'string'],
  ],
  'required' => [
    'title',
    'author',
    'isbn',
  ],
  'additionalProperties' => false,
];

$client->registerEventSchema($eventType, $schema);
```

## Listing Subjects

To list all subjects, call the `readSubjects` function with `/` as the base subject. The function returns an asynchronous iterator, which you can use e.g. inside a `foreach` loop:

```php
$subjects = $client->readSubjects('/');

foreach($subjects as $subject) {
  // ...
}
```

If you only want to list subjects within a specific branch, provide the desired base subject instead:

```php
$subjects = $client->readSubjects('/books');

foreach($subjects as $subject) {
  // ...
}
```

### Aborting Listing

If you need to abort listing use `abortIn` before or within the `foreach` loop. The `abortIn` method expects the abort time in seconds. However, this only works if there is currently an iteration going on:

```php
$subjects = $client->readSubjects('/');

$client->abortIn(0.1);
foreach($subjects as $subject) {
  // ...
  $client->abortIn(0.1);
}
```

## Listing Event Types

To list all event types, call the `readEventTypes` function. The function returns an asynchronous iterator, which you can use e.g. inside a `foreach` loop:

```php
$eventTypes = $client->readEventTypes();

foreach($eventTypes as $eventType) {
  // ...
}
```

### Aborting Listing

If you need to abort listing use `abortIn` before or within the `foreach` loop. The `abortIn` method expects the abort time in seconds. However, this only works if there is currently an iteration going on:

```php
$eventTypes = $client->readEventTypes();

$client->abortIn(0.1);
foreach($eventTypes as $eventType) {
  // ...
  $client->abortIn(0.1);
}
```

## Listing a Specific Event Type *(Requires EventSourcingDB 1.1)*

To list a specific event type, call the `readEventType` function with the event type as an argument. The function returns the detailed event type, which includes the schema:

```php
$eventType = $client->readEventType('io.eventsourcingdb.library.book-acquired');
```

## Verifying an Event's Hash *(Added in 1.1)*

To verify the integrity of an event, call the `verifyHash` function on the event instance. This recomputes the event's hash locally and compares it to the hash stored in the event. If the hashes differ, the function returns an error:

```php
$event->verifyHash();
```

*Note that this only verifies the hash. If you also want to verify the signature, you can skip this step and call `verifySignature` directly, which performs a hash verification internally.*

## Verifying an Event's Signature *(Added in 1.1; Requires EventSourcingDB 1.1)*

To verify the authenticity of an event, call the `verifySignature` function on the event instance. This requires the public key that matches the private key used for signing on the server.

The function first verifies the event's hash, and then checks the signature. If any verification step fails, it returns an error:

```php
$verificationKey = // an ed25519 public key

$event->verifySignature($verificationKey);
```

## Using Testcontainers

Import the `Container` class, call the `start` function to run a test container, get a client, run your test code, and finally call the `stop` function to stop the test container:

```php
require __DIR__ . '/vendor/autoload.php';

use Thenativeweb\Eventsourcingdb\Container;

$container = new Container();
$container->start();

$client = $container->getClient();

// ...

$container->stop();
```

To check if the test container is running, call the `isRunning` function:

```php
$isRunning = $container->isRunning();
```

### Configuring the Container Instance

By default, `Container` uses the `latest` tag of the official EventSourcingDB Docker image. To change that, call the `withImageTag` function:

```php
use Thenativeweb\Eventsourcingdb\Container;

$container = new Container()
  ->withImageTag('1.0.0');
```

Similarly, you can configure the port to use and the API token. Call the `withPort` or the `withApiToken` function respectively:

```php
use Thenativeweb\Eventsourcingdb\Container;

$container = new Container()
  ->withPort(4000)
  ->withApiToken('secret');
```

*(Added in 1.1; Broken in 1.1, fixed in 1.3)* If you want to sign events, call the `withSigningKey` function. This generates a new signing and verification key pair inside the container:

```php
$container = new Container()
  ->withSigningKey();
```

You can retrieve the private key (for signing) and the public key (for verifying signatures) once the container has been started:

```php
$signingKey = $container->getSigningKey();
$verificationKey = $container->getVerificationKey();
```

The `signingKey` is the private key EventSourcingDB signs events with. The `verificationKey` can be passed to `verifySignature` when verifying events read from the database.

### Configuring the Client Manually

In case you need to set up the client yourself, use the following functions to get details on the container:

- `getHost()` returns the host name
- `getMappedPort()` returns the port
- `getBaseUrl()` returns the full URL of the container
- `getApiToken()` returns the API token

## Further Resources

- **Repository**: **[thenativeweb/eventsourcingdb-client-php](https://github.com/thenativeweb/eventsourcingdb-client-php)**
- **Registry**: **[Packagist](https://packagist.org/packages/thenativeweb/eventsourcingdb)**
- **License (MIT)**: **[License file](https://github.com/thenativeweb/eventsourcingdb-client-php/blob/main/LICENSE.md)**
- **Issue tracker**: **[GitHub Issues](https://github.com/thenativeweb/eventsourcingdb-client-php/issues)**