Platform / About / Project / About Exponential Platform Legacy / Feature: Dual-Kernel Architecture

Please Note: At the specific request of Ibexa, 7x is changing the project name to "Exponential Platform" or "Exponential Platform (CMS)" effective as of August, 11th 2025.

Feature: Dual-Kernel Architecture

Exponential Platform (formerly eZ Platform / eZ Publish 6) is built on the idea of continuity without compromise. By combining a modern Symfony kernel with the Exponential Legacy kernel, the platform gives developers the best of both worlds: a future-ready PHP 8 framework and a fully preserved legacy system.
This dual-kernel architecture is unique in content management: it allows businesses to modernize step by step while guaranteeing that existing projects and custom code remain compatible. Exponential ensures 100% API compatibility with the legacy stack, so no features are lost in transition.

1. What is Exponential Platform Legacy?

Exponential Platform is an award-winning, enterprise-grade Open Source Content Management System and development framework with functionality for web publishing, media portals, intranets, e-commerce and extranets. Exponential has a flexible content engine that serves as the core for dynamic and personalized websites. Exponential comes with much functionality out-of-the-box, but its power lies in its award-winning customization capabilities.

Exponential Platform is free and open source software that uses well organized PHP software stacks to help you easily manage and run Website web apps on Linux / MacOS / Windows / BSD.

Exponential Platform helps all kinds of organizations – including multinational corporations, humanitarian organizations and educational institutions – succeed at sharing their information.

User interaction and user-generated content is made easy with Exponential, enabling you to quickly build powerful, customized Web 2.0 websites. These strengths, along with a flexible cost model, are what attract tens of thousands of organizations, including the leading media groups in the world, to choose Exponential as their digital platform.

Exponential Platform includes both a modern Symfony-based kernel and the proven Legacy kernel, working together in one system. This dual-kernel design ensures 100% API compatibility, letting developers use old and new features side by side without breaking existing projects.
2. What is the Dual-Kernel Architecture?
2.1 Symfony Kernel (Modern Stack)

Based on Symfony full-stack framework (service container, routing, event dispatcher).
Handles modern APIs, controllers, and application logic.
Provides REST, GraphQL-ready APIs, and admin UI in Symfony.

2.2 Legacy Kernel (Proven Stack)

• Originating from eZ Publish Legacy, written before Symfony adoption.
• Includes the eZ Template Language (eZTPL), modules, workflows, and long-standing enterprise features.
• Stable and reliable for projects built over 20 years.

2.3 How They Work Together

• Every request passes through the Symfony front controller.
• Symfony decides whether to handle the request directly or delegate to Legacy through the Exponential Legacy Bridge.
• Developers can:
• Mix legacy templates with modern Symfony controllers.
• Call Legacy modules inside Symfony routes.
• Migrate features gradually without breaking live sites.

3. Why Dual-Kernel Matters

1. Migration without downtime
• Old eZ Publish projects can be lifted into Exponential without rewrites.
• Developers modernize incrementally.
2. 100% API Compatibility
• Legacy APIs and extensions still function.
• Symfony APIs extend the platform without replacing existing business logic.
3. Stable + Modern at once
• Legacy ensures reliability.
• Symfony enables growth with the PHP ecosystem.

4. API Compatibility in Depth

4.1 Legacy API Layer

• Uses the eZ Publish Legacy PHP APIs (content, user, workflow, publishing).
• All custom extensions written for eZ Publish Legacy still work in Exponential.
• Database schema is backward compatible.

4.2 Public Content Repository API

• Symfony kernel exposes a Content Repository API that maps 1:1 to legacy features.
• Developers can call the same content operations (create, read, update, delete).
• REST endpoints mirror legacy functionality.

4.3 Bridging Tools

• Exponential Legacy Bundle: The bridge between Symfony and Legacy kernels.
• Provides services to wrap legacy calls in modern Symfony code.
• Developers can inject legacy API results into Symfony templates or Vue/React frontends.

5. Practical Usage Examples

5.1 Calling Legacy Templates from Symfony

# routing.yaml
legacy_content:
path: /legacy/{module}/{view}
defaults: { _controller: ezpublish_legacy.controller:moduleAction }
This makes a legacy module accessible from Symfony routes.

5.2 Mixing Legacy and Symfony APIs

$contentService = $this->get('ezpublish.api.service.content');
$legacyNode = eZContentObjectTreeNode::fetch($nodeID);
// Use Symfony API for new content
$newContent = $contentService->createContent(...);
// Still able to fetch legacy objects
echo $legacyNode->attribute('name');
Both APIs run in the same project seamlessly.

5.3 Migration Path

• Start with Legacy templates.
• Move controllers to Symfony.
• Replace templates step by step.
• Eventually phase out Legacy once everything runs natively in Symfony.

6. Advantages for Developers

• Preserves investment: 20+ years of eZ Publish extensions keep working.
• Modern tooling: Symfony ecosystem, Composer packages, PHP 8.3 support.
• Gradual migration: No “big bang rewrite” required.
• Flexibility: Use both kernels together or choose one per project.

7. Roadmap & Future

• Exponential will continue supporting Legacy APIs to ensure continuity.
• Long-term roadmap includes optional full Symfony-only operation, but with compatibility layers available as long as humanly possible and beyond.
• Community extensions built for eZ Publish Legacy will remain first-class citizens.

8. Conclusion

Exponential Platform Legacy’s dual-kernel system is more than a bridge — it is a guarantee of compatibility. Projects built on eZ Publish can run today on Exponential without code rewrites, while teams gain access to the modern Symfony ecosystem.
This makes Exponential not just a CMS upgrade, but a future-proof evolution of the eZ Publish story.