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PHP Web Services

Cover of PHP Web Services by Lorna Jane Mitchell Published by O'Reilly Media, Inc.
  1. Preface
    1. Conventions Used in This Book
    2. Using Code Examples
    3. Safari® Books Online
    4. How to Contact Us
  2. 1. Introduction
  3. 2. HTTP
    1. Examining HTTP
      1. Curl
      2. Browser Tools
      3. PHP
  4. 3. Request and Response
    1. Clients and Servers
  5. 4. HTTP Verbs
    1. GET
    2. POST
    3. Other HTTP Verbs
  6. 5. Headers
    1. Request and Response Headers
    2. Common HTTP Headers
      1. User-Agent
      2. Headers for Content Negotiation
      3. Authorization
      4. Custom Headers
  7. 6. Cookies
    1. Cookie Mechanics
    2. Working With Cookies in PHP
  8. 7. JSON
    1. When to Choose JSON
    2. Handling JSON with PHP
    3. JSON in Existing APIs
  9. 8. XML
    1. When To Choose XML
    2. XML in PHP
    3. XML in Existing APIs
  10. 9. RPC and SOAP Services
    1. RPC
    2. SOAP
      1. WSDL
      2. PHP SOAP Client
      3. PHP SOAP Server
      4. Generating a WSDL File from PHP
      5. PHP Client and Server with WSDL
  11. 10. REST
    1. RESTful URLs
    2. Resource Structure and Hypermedia
    3. Data and Media Types
    4. HTTP Features in REST
      1. Create Resources
      2. Read Records
      3. Update Records
      4. Delete Records
    5. Additional Headers in RESTful Services
      1. Authorisation Headers
      2. Caching Headers
    6. RESTful vs Useful
  12. 11. Debugging Web Services
    1. Debug Output
    2. Logging
    3. Debugging From Outside Your Application
      1. Wireshark
      2. Charles Proxy
    4. Finding the Tool for the Job
  13. 12. Making Service Design Decisions
    1. Service Type Decisions
    2. Consider Data Formats
    3. Customisable Experiences
    4. Pick Your Defaults
  14. 13. Building a Robust Service
    1. Consistency is Key
      1. Consistent and Meaningful Naming
      2. Common Validation Rules
      3. Predictable Structures
    2. Making Design Decisions for Robustness
  15. 14. Error Handling in APIs
    1. Output Format
    2. Meaningful Error Messages
    3. What To Do When You See Errors
  16. 15. Documentation
    1. Overview Documentation
    2. API Documentation
    3. Interactive Documentation
    4. Tutorials and the Wider Ecosystem
  17. A. A Guide To Common Status Codes
  18. B. Common HTTP Headers
  19. About the Author
  20. Copyright

Chapter 5. Headers

So far we’ve seen various presentations of the HTTP format, and examined the idea that there is a lot more information being transferred in web requests and responses than just what appears in the body of the response. The body is certainly the important bit and often is the meatiest, but the headers give key pieces of information, both in requests and responses, that allow client and server to communicate effectively. If you think of the body of the request being the birthday card with a cheque inside it, then the headers are the address, postmark and perhaps the “do not open until …” instruction on the outside, see Figure 5-1.

This additional information is how we get the body data to where it needs to go and how we instruct the target what to do with it.

Image Envelope with stamp, address and postmark
Figure 5-1. Image Envelope with stamp, address and postmark

Request and Response Headers

Many of the headers you see in HTTP make sense both in requests and responses. Others might be specifc to either a request or a response. Here’s a sample set of real request and response headers from when I request my own site from a browser (I’m using Chrome):

Example request headers

GET / HTTP/1.1 Host: Connection: keep-alive Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 User-Agent: Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.19 (KHTML, like Gecko) Chrome/25.0.1323.1 ...

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