An implementation of a Correlation ID and a framework agnostic PSR 15-HTTP middlware.

A Correlation ID, also known as a Transit ID, is a unique identifier value that is attached to requests and messages that allow reference to a particular transaction or event chain. The Correlation Pattern, which depends on the use of Correlation ID is a well documented Enterprise Integration Pattern.

• The value of a correlation ID
• Identity Correlation on Wikipedia

The correlation ID is a singleton class that will always return the same ID for the current life-cycle of the request.

Calling CorrelationID::toString() will return a string and will return the same string for the whole live cycle of the application. You can compare a string to the Correlation ID by calling CorrelationID::sameAs('your-string').

By default it uses its internal implementation to generate a UUID v4 as value of the Correlation ID. If you are using ramsey/uuid, it will use it automatically.

The middleware will automatically put the correlation ID into your request object as attribute and header value. By default both use the CorrelationID name.

$middleware = new CorrelationIDMiddleware(
    CorrelationID::toString()
);

Since there is no standard for where this needs to be done, just add the correlation ID to your response where it suits your architecture or framework the best.

$response->withHeader('CorrelationID', CorrelationId::toString());

For Symfony there is a bundle available that will automatically make the Correlation ID available in the request and response object.

Licensed under the MIT license.

Copyright (c) Phauthentic / Florian Krämer