How to Connect Your Twilio Agent to External APIs with PHP

A Twilio tutorial explains how to build a PHP voice AI agent that uses Conversation Relay, OpenAI tool calling, and external REST APIs to provide real-time information and actions during phone conversations. Using PHP 8.5, OpenSwoole, Composer, ngrok, and a Twilio voice-enabled number, the example creates a WebSocket-based application that receives voice prompts, converts them into conversational messages, streams responses from OpenAI, and returns spoken text through Twilio. The demonstration configures an OpenAI function tool that retrieves a random fact from the unauthenticated Cat Facts API, with a system prompt requiring the model to call the API rather than invent facts. It also covers environment-variable configuration, TwiML setup for incoming calls, session and interruption handling, API error handling, exposing the local server with ngrok, and configuring the Twilio phone-number webhook. The approach can be extended to authenticated services such as customer databases, inventory systems, calendars, and booking platforms, enabling voice agents to access live data and perform customer-facing tasks.

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