OpenAI API Client in PHP Files

What's Changed

• Response Object: Added getLastResponse() returning a Response object with ->status(), ->ok(), ->headers(), ->header($name), ->body(), and ->json() for easy inspection without manual json_decode().
• Exception Handling: Added setThrowOnError(true) and OpenAiException for throwing on HTTP 4xx/5xx responses with status code, error type, and error code.
• Automatic Retries: Added setRetries(maxRetries, baseDelayMs) with exponential backoff, jitter, and Retry-After header support for rate limits (429) and transient server errors (5xx on idempotent methods).
• Static Analysis & Types: Added PHPStan (level 5) and typed PHPDoc shape annotations on core methods while strictly preserving PHP 7.4+ compatibility with zero runtime dependencies.
• Decisions Usage: Added getDecisionsUsage() reporting endpoint.
• Pure Tests: Removed mock echo-server tests in favor of pure in-memory unit tests and real API tests.

Full Changelog: https://github.com/orhanerday/open-ai/compare/6.2.0...6.3.0