FusionPBX

FusionPBX is a self‑hosted, multi‑tenant Voice over IP (VoIP) platform built on top of FreeSWITCH. It exposes a rich set of telephony services—PBX, carrier‑grade switching, call center, fax, voicemail, conferencing, and a flexible appliance framework—while keeping the core logic in PHP and SQL. For developers, this means a familiar web‑app stack that orchestrates complex real‑time audio flows via FreeSWITCH’s event bus and XML configuration.

Technical Stack & Architecture

• Core Engine: FreeSWITCH (C, event‑driven, multi‑threaded) handles media processing, SIP signaling, and call routing.
• Web Interface & API: PHP 7/8 runs the FusionPBX web UI, providing REST‑style endpoints (JSON) for CRUD operations on extensions, trunks, dialplans, and user accounts.
• Database: MySQL/MariaDB stores configuration, call detail records (CDRs), and user data. The schema is auto‑generated on install but can be extended via custom tables.
• Real‑time Features: WebSockets deliver live call state, CPU usage, and active call lists to the UI without polling.
• Autoloading: Composer‑style autoloader loads PHP classes on demand, keeping the codebase modular.

The architecture follows a thin‑client pattern: PHP renders configuration pages, while FreeSWITCH runs as a daemon that reads XML dialplan files generated by FusionPBX. This separation allows developers to tweak FreeSWITCH directly or rely on the web UI for most tasks.

Core Capabilities & APIs

• Dialplan Management: Dynamic XML generation, priority manipulation, and custom application hooks.
• User & Extension Provisioning: REST endpoints to create extensions, assign VoIP devices, and generate provisioning files (XML, JSON).
• Call Detail Records: Full CDR export with call‑flow icons; APIs to query by time, caller, callee, or application.
• Webhooks & Callbacks: Trigger external services on events such as call start, end, or voicemail creation.
• Plugin System: Add‑ons like dialplan_tools and device_logs extend functionality without altering core code.
• OpenID & OAuth: Optional authentication modules for SSO integration.

Deployment & Infrastructure

FusionPBX is docker‑friendly; official images expose FreeSWITCH and PHP behind Nginx/Apache, making it easy to spin up a multi‑tenant environment. For high availability, replicas can share a common MySQL cluster and use FreeSWITCH’s built‑in SIP federation. Scaling is horizontal: add more PHP workers or FreeSWITCH instances behind a load balancer, and the database layer can be sharded or replicated.

Integration & Extensibility

Developers can integrate FusionPBX with external systems via:

• REST APIs: CRUD on extensions, trunks, and call routing.
• Webhooks: Push events to CRM or ticketing systems.
• SIP Trunking: Connect to any SIP provider, or expose a trunk for other services.
• Custom Dialplan Applications: Write FreeSWITCH XML or C modules that plug into the call flow.
• Database Hooks: Trigger stored procedures on new CDRs for billing or analytics.

Developer Experience

• Documentation: The README, API references, and wiki provide a solid foundation; however, the community forums are often the quickest source for edge‑case questions.
• Configuration: Most settings are exposed through the web UI; advanced users can tweak FreeSWITCH XML directly.
• Community: A vibrant, active community contributes add‑ons and shares custom scripts on GitHub and forums.
• Licensing: FusionPBX is open‑source (GPL), allowing unrestricted modification and redistribution—ideal for SaaS or internal tooling.

Use Cases

1. Enterprise PBX – Replace legacy on‑prem phones with a cloud‑like, multi‑tenant system while keeping control of the infrastructure.
2. Call Center Platform – Leverage built‑in queues, real‑time monitoring, and CDR analytics to build a fully integrated contact center.
3. VoIP API Service – Expose SIP trunking and REST APIs to developers building messaging or telephony features into their apps.
4. Educational / Lab Environments – Rapidly spin up isolated PBX instances for training or testing SIP clients.

Advantages Over Alternatives

FusionPBX offers a developer‑friendly blend of a web‑based configuration layer and a powerful real‑time telephony engine, making it an attractive choice for building customized communication solutions or SaaS telephony platforms.