Senior PHP Developer for AI Platform

I am looking for a highly skilled PHP developer with strong experience in AI/LLM integration to build a complex web-based platform. This is not a simple chatbot or API wrapper project. The goal is to create a production-ready AI workflow system in PHP that can handle multi-step task execution, document analysis, tool calling, workflow management, and secure AI-driven automation.

Scope of Work:
The selected freelancer will design and develop a PHP-based application, preferably using Laravel or Symfony, with clean architecture, scalability, and strong security practices. The system should allow users to submit tasks that are processed through multiple AI-driven stages such as planning, analysis, retrieval, validation, and reporting.

The platform should support:
- Multi-step AI workflows
- Role-based AI agents (planner, analyst, reviewer, summarizer, etc.)
- Secure tool/function calling
- Document upload and retrieval-based AI responses
- Execution logs and workflow history
- Human approval checkpoints for sensitive actions
- Error handling, retries, and resumable processing

Technical Requirements:
The backend must be built in **modern PHP** with a structured and maintainable codebase.
Preferred stack includes:
- PHP 8+
- Laravel or Symfony
- PostgreSQL or MySQL
- Redis for queues/cache
- Dockerized setup
- Integration with OpenAI or similar LLM APIs
- Vector database or pgvector support for document retrieval

The solution should include:
1. Workflow Engine
A configurable engine to define and execute multi-step AI workflows.

2. AI Agent Orchestration
Support for multiple AI roles with different prompts, permissions, and output rules.

3. Tool Execution Layer
Safe execution of approved internal or external functions requested by the AI.

4. Document Processing / RAG
Upload, parse, chunk, embed, and retrieve information from files such as PDF, DOCX, TXT, and HTML.

5. Observability
Full logging of workflow steps, AI responses, tool calls, failures, retries, and costs.

6. Security
Input validation, role-based permissions, prompt injection protection, secure API key handling, and audit logs.

Deliverables:
The freelancer must provide:
- Full source code
- Database schema and migrations
- API documentation
- Docker setup
- Sample workflows
- Test suite
- Deployment guide
- Technical architecture documentation

Important Notes:
This is a high-difficulty project intended for experienced developers only. Please do not apply if your background is limited to basic chatbot development or simple API integrations. I am specifically looking for someone who can build a secure, scalable, and production-grade AI platform in PHP.