How to Make ChatGPT Codex Work with PHP and Symfony

Codex is a cloud-based coding agent created by OpenAI that can run multiple tasks in parallel, including fixing bugs, implementing features, and suggesting improvements. Although Codex works well with PHP, its most powerful feature is running code to verify proposed changes, which is not natively supported for PHP. This article explains how to make Codex work effectively with PHP and Symfony applications. To set up Codex, users need to create an environment for their repository, which defines how Codex interacts with their code. The setup script is critical for PHP/Symfony projects, as it installs PHP, Composer, and other tools not included in the default image. The script runs at the beginning of every task and prepares the environment for development and testing. For private Composer packages, users need to authenticate Composer by creating a personal access token and adding it to Codex. If the test suite requires a database, users need to install and configure it in the setup script. Once configured, Codex becomes a real coding assistant that understands the stack and validates its own changes. By following these steps, users can unlock full task automation in Symfony and PHP projects.