Child themes are a simple but powerful way to customize a pre-made theme. Learning how to use them properly means you’ll never risk losing all your modifications when the developer releases a new version and you update the theme. Using easy-to-follow language, I’ll walk you through the steps to set up a child theme and we’ll get started making some tweaks – from CSS look-and-feel adjustments to more substantial changes in functionality.

1. Kathryn Presner
WordCamp Montreal 2014
@zoonini
#wcmtl

2. Kathryn Presner
Happiness Engineer
Automattic Theme Team

3. https://www.flickr.com/photos/ben124/5396260658

4. https://www.flickr.com/photos/sackton/8258253775/

5. Brownies
Cream butter and sugar.
Beat in eggs and vanilla.
Add dry ingredients.
Spread in pan, bake at
350F for 30 min.
1 cup sugar
½ cup butter
2 eggs
1 tsp vanilla
1 cup flour
¼ cup cocoa
½ tsp. salt

6. Child theme = recipe variation
https://www.flickr.com/photos/snekse/399462304

7. Brownie Variations
Blondies
+ brown sugar - white sugar
Mint brownies
+ add mint extract - vanilla
Nutty brownies
+ nuts
Double chocolate mini muffins
+ choc. chips +bake in mini-muffin tin

8. https://www.flickr.com/photos/handcoding/2117794703

14. Parent Theme
!=
Starter Theme

24. Why?

25. Why?
Faster development

26. Why?
Benefit from others' design, coding

27. Why?
Safer updates

29. Why not?

30. Why not?
Untangling others' code

31. Why not?
Can feel hacky

32. Why not?
Can be inefficient

33. http://wordpress.org/themes/

34. Sorbet

35. One-minute
child theme setup
For reals!

36. Setup
parent

37. Setup
parent
child

38. Setup
parent
child

39. Setup
parent
child

40. Setup
required file

41. style.css

42. style.css

43. Activate child theme

44. Import parent styles
in style.css

45. (or) Enqueue styles
in functions.php

46. https://www.flickr.com/photos/47741487@N06/7994654729

53. https://www.flickr.com/photos/healthcare4every1/3743271846

54. Template files
YES
Use child's file
NO
Use parent's file
Does template file exist in child theme?

55. and
so
on
...

57. content.php

58. content.php

59. content.php in parent

60. content.php in child
https://codex.wordpress.org/Post_Formats#Using_Formats

62. Create custom template
http://codex.wordpress.org/Page_Templates#Creating_a_Page_Template

64. https://www.flickr.com/photos/stefz/2159280574

65. Functions – loading order
1. Child's functions.php loaded
2. Parent's functions.php loaded

66. Duplicate functions

68. Hooks, actions, filters
https://www.flickr.com/photos/bonitoclub/7959426472

69. Remember this?

70. https://www.flickr.com/photos/nationalzoo/4368143044

71. Grandchild
themes?
https://www.flickr.com/photos/nationalzoo/4368143044

72. Resources
Child Themes – Codex
https://codex.wordpress.org/Child_Themes
Conditional Tags – Codex
http://codex.wordpress.org/Conditional_Tags
Functions – Codex
https://codex.wordpress.org/Function_Reference/

73. Resources
ThemeShaper
http://themeshaper.com
Replacing a filter in a Twenty Twelve Child
Theme
http://mikelittle.org/replacing-a-filter-in-a-twenty-twelve-
child-theme/
Creating Grandchild Themes
http://docs.appthemes.com/tutorials/creating-grandchild-
themes/

74. Credits
Presentation
slideshare.net/zoonini
Kathryn Presner
kpresner.com / Twitter: @zoonini
Fonts
Arvo & Lato
Photos
Flickr – Creative Commons
Cat photos – K. "Crazy Cat Lady" Presner