This document discusses the importance of backwards compatibility and maintaining consistency across versions. It provides examples of how backwards compatibility can be broken in areas like functions, CSS classes, file paths, and metadata. The document also discusses a case study of how Easy Digital Downloads addressed backwards compatibility when changing their download link URLs to reduce potential breakage across 40,000+ active sites. Maintaining backwards compatibility takes effort but is important to avoid breaking existing functionality for users.

1. Backwards
Compatibility
taking it seriously

2. What is it?

3. Not breaking things
from version to version

4. Maintaining methods
method v1 still works with method v2

5. Keeping consistency
design, database schema, markup, etc

6. Basic examples

7. PHP

8. function do_thi_thing() { }
version 1.0

9. function do_this_thing() { }
version 2.0

10. Fatal error
undefined function: do_thi_thing()

11. function do_thi_thing() { return do_this_thing(); }
Solution:

12. CSS / HTML

13. .entry { background: #f0f0f0 }
<div class=“entry”>

14. .entry { background: #f0f0f0 }
<div class=“post”>

15. No more #f0f0f0
Oops

16. <div class=“post entry”>
Solution:

17. Filenames

18. require_once ‘includes/class-authors.php’;
class-authors.php

19. require_once ‘includes/class-authors.php’;
class-vendors.php

20. Fatal error
file not found

21. Metadata
get_post_meta( $post_id, ‘city_name’, true );
value: New York

22. Metadata
get_post_meta( $post_id, ‘city’, true );
value:

23. function pw_filter_old_meta( $check, $object_id, $meta_key, $single ) {
if( 'city_name' === $meta_key ) {
$check = get_post_meta( $object_id, 'city', $single );
}
return $check;
}
add_filter( 'get_post_metadata', 'pw_filter_old_meta', 10, 4 );
Solution:

24. Solution:
get_post_meta( $post_id, ‘city’, true );
value: New York
get_post_meta( $post_id, ‘city_name’, true );
value: New York

25. So many more

26. How easy is it?

27. Why worry about it?

28. What’s the benefit?

29. Does it slow you
down?

30. Case Study

31. EDD Signed URLs
longest outstanding issue for EDD, 12/19/2012
2.3 released 3 days ago - how’d we do?

32. Old Method
http://edd/index.php?download_key={key}&email={email}&file=fil
e}&price_id={price}&download_id={id}&expire={expire}
http://edd/index.php?download_key=7211cce2df06b572890934
752a4c0896&email=pippin%40pippinsplugins.com&file=1&price
_id=1&download_id=514&expire=MTQyNDE2NzcyOQ%3D%3D

33. New Method
http://edd/index.php?eddfile={file}&ttl={expre}&token={tok
en}
http://edd/index.php?eddfile=2231%3A514%3A0&ttl=142
4167604&token=4d0a86fb8f8be40cf9927222076a5ced

34. Potential Breakage
let’s consider the possibilities

35. 40,000+ active sites
basic assumptions:

36. 40,000+ active sites
basic assumptions:
50 customers per site

37. 40,000+ active sites
basic assumptions:
50 customers per site
1 sale per customer / 1 download link per customer

38. 40,000+ active sites
basic assumptions:
50 customers per site
1 sale per customer / 1 download link per customer
50*40,000 = 2,000,000 broken download links

39. 40,000+ active sites
basic assumptions:
50 customers per site
1 sale per customer / 1 download link per customer
50*40,000 = 2,000,000 broken download links
…..

40. 40,000+ active sites
basic assumptions:
50 customers per site
1 sale per customer / 1 download link per customer
50*40,000 = 2,000,000 broken download links
…..
probably vastly under exaggeration

41. Challenge accepted
programming is all about challenges

42. Make it a goal

43. Mentality
great development is more about how it is thought out
than how it is done
your attitude and dedication will go further than your
knowledge of syntax

44. “I will”

45. Thanks
Pippin Williamson
pippinsplugins.com - @pippinsplugins