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Purpose and Goals

The Instructor HTTP client API is designed to provide a consistent interface for making HTTP requests across different PHP environments. It provides a single API regardless of the underlying HTTP client available in the given environment, which may be Symfony, Laravel, Slim, or just vanilla PHP. The primary goals of the API are:
  • Easily Switch Between HTTP Clients: Allow developers to switch between different HTTP client libraries (like Guzzle, Symfony, and Laravel) without changing the code that makes HTTP requests
  • Framework Agnostic: Work seamlessly in Laravel, Symfony, or any PHP application without framework-specific dependencies
  • Consistent Interface: Provide a one way to make HTTP requests regardless of the underlying client library
  • Middleware Support: Enable easy extension through a powerful middleware system
  • Adaptability: Allow switching between different HTTP client implementations with minimal code changes
  • Streaming Support: Provide first-class support for streaming responses, which is crucial for LLM interactions
  • Concurrency: Support parallel requests through request pooling
By abstracting away the differences between various HTTP client libraries, the Instructor works across different environments and frameworks without modification.

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Key Features

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Multiple Client Support

The API supports multiple HTTP client libraries through specialized drivers:
  • Guzzle: A popular and feature-rich HTTP client for PHP
  • Symfony HTTP Client: The HTTP client component from the Symfony framework
  • Laravel HTTP Client: The HTTP client built into the Laravel framework

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Middleware System

A powerful middleware architecture allows for:
  • Request Pre-processing: Modify requests before they are sent
  • Response Post-processing: Transform or analyze responses
  • Response Streaming: Process streaming responses chunk by chunk
  • Debugging: Log requests and responses for troubleshooting
  • Custom Behaviors: Add specialized behaviors like caching or rate limiting

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Streaming Response Support

First-class support for streaming HTTP responses, which is essential for:
  • LLM Text Generation: Process token-by-token responses from AI models
  • Large File Downloads: Handle large files without excessive memory usage
  • Real-time Data: Process server-sent events or other real-time data streams

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Request Pooling

Execute multiple HTTP requests concurrently for better performance:
  • Concurrent Execution: Send multiple requests in parallel
  • Configurable Concurrency: Control the maximum number of concurrent requests
  • Result Collection: Process results as they arrive
  • Error Handling: Flexible error handling strategies

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Flexible Configuration

Comprehensive configuration options:
  • Per-Client Configuration: Different settings for each client type
  • Named Configurations: Multiple configurations for different use cases
  • Runtime Configuration: Change configuration during execution
  • Timeout Controls: Fine-grained control over various timeout settings

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Debug and Testing Support

Built-in features for debugging and testing:
  • Request/Response Logging: Detailed logging of HTTP interactions
  • Mock Client: Test your code without making actual HTTP requests
  • Record/Replay: Record HTTP interactions and replay them later

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Architecture Overview

The Instructor HTTP client follows a layered architecture with several key components:

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Client Layer

The HttpClient class serves as the main entry point and provides a fluent interface for configuring and using the HTTP client. 
HttpClient
  └── using() - Create client with specific configuration (static)
  └── default() - Create client with default configuration (static)
  └── withMiddleware() - Add middleware components
  └── withMiddlewareStack() - Replace entire middleware stack
  └── withoutMiddleware() - Remove middleware by name
  └── withRequest() - Create pending request for execution
  └── pool() - Execute multiple requests concurrently
  └── withPool() - Create pending pool for deferred execution
// @doctest id="06c2"

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Middleware Layer

The middleware system allows for processing requests and responses through a chain of handlers: 
Request -> Middleware 1 -> Middleware 2 -> ... -> Driver -> External API
                                                   ↓
Response <- Middleware 1 <- Middleware 2 <- ... <- Driver <- HTTP Response
// @doctest id="9abf"
Key components:
  • MiddlewareStack: Manages the collection of middleware
  • MiddlewareHandler: Orchestrates the middleware chain execution
  • BaseMiddleware: Base class for implementing middleware

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Driver Layer

Drivers implement the CanHandleHttpRequest interface and adapt different HTTP client libraries: 
CanHandleHttpRequest (interface)
  ├── GuzzleDriver
  ├── SymfonyDriver
  ├── LaravelDriver
  └── MockHttpDriver (for testing)
// @doctest id="ccd7"

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Adapter Layer

Response adapters convert client-specific responses to a common interface: 
HttpResponse (interface)
  ├── PsrHttpResponse (Guzzle)
  ├── SymfonyHttpResponse
  ├── LaravelHttpResponse
  └── MockHttpResponse
// @doctest id="e1cc"

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Supported HTTP Clients

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Guzzle HTTP Client

The Guzzle HTTP Client is a powerful HTTP client library for PHP. It provides:
  • PSR-7 HTTP message implementation
  • Middleware system
  • Request and response plugins
  • HTTP/2 support (via cURL)
The GuzzleDriver adapts Guzzle to the Instructor HTTP client API interface.

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Symfony HTTP Client

The Symfony HTTP Client is a component of the Symfony framework. Features include:
  • HTTP/2 push support
  • PSR-18 compatibility
  • Automatic content-type detection
  • Proxy support
The SymfonyDriver adapts the Symfony HTTP Client to the Instructor HTTP client API.

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Laravel HTTP Client

The Laravel HTTP Client is built into the Laravel framework and provides:
  • Fluent, readable syntax
  • Request macros
  • Automatic JSON handling
  • Rate limiting
  • Retry logic
The LaravelDriver adapts the Laravel HTTP Client to the Instructor HTTP client API.

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Mock HTTP Driver

The MockHttpDriver provides a test double for unit testing. It doesn’t make actual HTTP requests but returns predefined responses based on matching rules.
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