Great question on the developer message! The best resource to read more is our Model Spec detailing the hierarchy:
Follow the chain of command. Subject to its rules, the Model Spec explicitly delegates all remaining power to the developer (for API use cases) and end user. In some cases, the user and developer will provide conflicting instructions; in such cases, the developer message should take precedence.
Thank you for the note on PHP! With the addition of Java and Go today, our goal is to ultimately support the most popular languages and tech stacks. No timeline to share yet for a PHP SDK, but in the meantime, we recommend community-supported libraries to get started.