my personal

1. Getting Into The Loop
mitcho (Michael 芳貴 Erlewine)
http://mitcho.com
January 23, 2010
WordCamp Boston

2. Today
• Introduction
• Loop basics
• Custom queries
• Method 1: Roll your own query
• Method 2: Filter every query
• Next steps

3. Today
NOTE:
• Will link to slides and code later
on http://mitcho.com/blog/
• Please rate later on SpeakerRate
(find link on the blog)

4. Today
• Introduction
• Loop basics
• Custom queries
• Method 1: Roll your own query
• Method 2: Filter every query
• Next steps

5. Introduction

6. Introduction
• Hi, I’m mitcho.

7. Introduction
• Hi, I’m mitcho.
• Linguist, coder, teacher.

8. Introduction
• Hi, I’m mitcho.
• Linguist, coder, teacher.
• At MIT. Previously at Mozilla. Now
working with Automattic.

9. Introduction
• Hi, I’m mitcho.
• Linguist, coder, teacher.
• At MIT. Previously at Mozilla. Now
working with Automattic.
• Programming PHP/MySQL since
2002?

10. Introduction
• Hi, I’m mitcho.
• Linguist, coder, teacher.
• At MIT. Previously at Mozilla. Now
working with Automattic.
• Programming PHP/MySQL since
2002?
• Blogging (off and on) since 2007.

11. Introduction
• Hi, I’m mitcho.
• Linguist, coder, teacher.
• At MIT. Previously at Mozilla. Now
working with Automattic.
• Programming PHP/MySQL since
2002?
• Blogging (off and on) since 2007.
• http://mitcho.com;
@mitchoyoshitaka

12. Introduction

13. Introduction
• Yet Another Related Posts Plugin

14. Introduction
• Yet Another Related Posts Plugin
• ...aka YARPP

15. Introduction
• Yet Another Related Posts Plugin
• ...aka YARPP
• As seen on Laughing Squid, ma.tt...

16. Introduction
• Yet Another Related Posts Plugin
• ...aka YARPP
• As seen on Laughing Squid, ma.tt...
• Over 350k downloads

17. Introduction
• Yet Another Related Posts Plugin
• ...aka YARPP
• As seen on Laughing Squid, ma.tt...
• Over 350k downloads
• http://mitcho.com/code/yarpp or
search for “YARPP”; @yarpp

18. Today
• Introduction
• Loop basics
• Custom queries
• Method 1: Roll your own query
• Method 2: Filter every query
• Next steps

19. The Loop

20. The Loop
• “The Loop” is the mechanism by
which posts are called from the
database and then displayed.

21. The Loop
• “The Loop” is the mechanism by
which posts are called from the
database and then displayed.
• On many pages—like the index or
archives—it “loops” through each
post.

22. The simplest Loop
get_header();
if (have_posts()) :
while (have_posts()) :
the_post();
the_content();
endwhile;
endif;
get_sidebar();
get_footer();

23. The simplest Loop
get_header();
if (have_posts()) :
{
while (have_posts()) :
the_post();
“The Loop” the_content();
endwhile;
endif;
get_sidebar();
get_footer();

24. The simplest Loop
get_header();
if (have_posts()) :
{
while (have_posts()) :
“The Loop”
the_post(); Sets up the post
the_content();
endwhile;
endif;
get_sidebar();
get_footer();

25. The simplest Loop
get_header();
if (have_posts()) :
{
while (have_posts()) :
“The Loop”
the_post(); Sets up the post
the_content();
endwhile;
endif;
get_sidebar();
get_footer();
Every theme’s PHP files are built on this
basic structure.

26. The Loop
if there are posts
while there are posts
get the post
do stuff with it
end while
end if

27. The Loop
if there are posts
{
while there are posts
get the post
“The Loop”
do stuff with it
end while
end if

28. The Loop

29. The Loop
• The Loop is where you can use
Template Tags.

30. The Loop
• The Loop is where you can use
Template Tags.
• codex.wordpress.org/
Template_Tags

31. The Loop
• The Loop is where you can use
Template Tags.
• codex.wordpress.org/
Template_Tags
• It’s the the_post() call that makes that
possible.

32. The Loop
if there are posts
while there are posts
get the post
do stuff with it
end while
end if
CC BY flickr.com/photos/myklroventine/
1430113497/

33. The Loop
But mommy, where do
posts come from?
if there are posts
while there are posts
get the post
do stuff with it
end while
end if
CC BY flickr.com/photos/myklroventine/
1430113497/

34. The Loop
But mommy, where do
posts come from?
if there are posts
while there are posts
get the post
do stuff with it
end while
end if
CC BY flickr.com/photos/myklroventine/
1430113497/

35. Every Loop has a query

36. Every Loop has a query
• Regularly, WordPress chooses the
right template file and query based on
your URL.

37. Every Loop has a query
• Regularly, WordPress chooses the
right template file and query based on
your URL.
• codex.wordpress.org/
Template_Hierarchy

38. Every Loop has a query
• Regularly, WordPress chooses the
right template file and query based on
your URL.
• codex.wordpress.org/
Template_Hierarchy
• /archives/123 → single post

39. Every Loop has a query
• Regularly, WordPress chooses the
right template file and query based on
your URL.
• codex.wordpress.org/
Template_Hierarchy
• /archives/123 → single post
• /archives→ archives

40. Every Loop has a query
• Regularly, WordPress chooses the
right template file and query based on
your URL.
• codex.wordpress.org/
Template_Hierarchy
• /archives/123 → single post
• /archives→ archives
• /tags/chicken→ all chicken articles

41. Today
• Introduction
• Loop basics
• Custom queries
• Method 1: Roll your own query
• Method 2: Filter every query
• Next steps

42. Customizing The
Loop

43. Customizing The
Loop
• Themes control how information
is presented...

44. Customizing The
Loop
• Themes control how information
is presented...
• The query controls what
information is presented.

45. Custom queries

46. Custom queries
Possible applications:

47. Custom queries
Possible applications:
• Create custom feeds/displays

48. Custom queries
Possible applications:
• Create custom feeds/displays
• ephramzerb.com/projects/feed-
wrangler/

49. Custom queries
Possible applications:
• Create custom feeds/displays
• ephramzerb.com/projects/feed-
wrangler/
• Pull information on other posts
from within the theme’s Loop

50. Custom queries
Possible applications:
• Create custom feeds/displays
• ephramzerb.com/projects/feed-
wrangler/
• Pull information on other posts
from within the theme’s Loop
• Customize what information is
displayed globally

51. Custom queries
Possible applications:
• Create custom feeds/displays
• ephramzerb.com/projects/feed-
wrangler/
• Pull information on other posts
Today’s
from within the theme’s Loop
examples • Customize what information is
displayed globally

52. Today
• Introduction
• Loop basics
• Custom queries
• Method 1: Roll your own query
• Method 2: Filter every query
• Next steps

53. Roll your own query

54. Roll your own query
EX:

55. Roll your own query
EX:
• Pull information on other posts
from within the theme’s Loop

56. Roll your own query
EX:
• Pull information on other posts
from within the theme’s Loop
• Display other posts with a specific
criteria, like a tag.

57. Roll your own query
EX:
• Pull information on other posts
from within the theme’s Loop
• Display other posts with a specific
criteria, like a tag.
• Wrap it up in a shortcode [others]

58. Roll your own query

59. Roll your own query
The idea:

60. Roll your own query
The idea:
• Create a new WP_Query object.

61. Roll your own query
The idea:
• Create a new WP_Query object.
• Given a $tag...

62. Roll your own query
The idea:
• Create a new WP_Query object.
• Given a $tag...
• new WP_Query(array('tag'=>
$tag))

63. Roll your own query
The idea:
• Create a new WP_Query object.
• Given a $tag...
• new WP_Query(array('tag'=>
$tag))
• Call it $my_query

64. Roll your own query
The idea:
• Create a new WP_Query object.
• Given a $tag...
• new WP_Query(array('tag'=>
$tag))
• Call it $my_query
• Create a Loop for $my_query

65. Roll your own query
The idea:
• Create a new WP_Query object.
• Given a $tag...
• new WP_Query(array('tag'=>
$tag))
• Call it $my_query
• Create a Loop for $my_query
• Do stuff in it

66. Make your own Loop
Make sure the Loop controllers are
using $my_query, not the default
($wp_query)
if ($my_query->have_posts()) :
while ($my_query->have_posts()) :
$my_query->the_post();
the_content();
endwhile;
endif;

67. The result:

68. DEMO:

69. More about WP_Query

70. More about WP_Query
Learn more from the Codex:

71. More about WP_Query
Learn more from the Codex:
• More information on the
parameters:

72. More about WP_Query
Learn more from the Codex:
• More information on the
parameters:
• codex.wordpress.org/
Template_Tags/query_posts

73. More about WP_Query
Learn more from the Codex:
• More information on the
parameters:
• codex.wordpress.org/
Template_Tags/query_posts
• Tips and examples:

74. More about WP_Query
Learn more from the Codex:
• More information on the
parameters:
• codex.wordpress.org/
Template_Tags/query_posts
• Tips and examples:
• codex.wordpress.org/The_Loop

75. Today
• Introduction
• Loop basics
• Custom queries
• Method 1: Roll your own query
• Method 2: Filter every query
• Next steps

76. Filter every query

77. Filter every query
EX:

78. Filter every query
EX:
• Customize what information
is displayed globally.

79. Filter every query
EX:
• Customize what information
is displayed globally.
• Hide all my tweets.

80. Filter every query

81. Filter every query
The idea:

82. Filter every query
The idea:
• Use the request filter to specify
that we don’t want results from
the “tweet” category (#10)

83. The result:

84. DEMO

85. Aside: the tools
Turn up the fire!
• Firefox getfirefox.com
• Firebug getfirebug.com
• FirePHP firephp.org

86. Aside: the tools
Turn up the fire!
• Firefox getfirefox.com
• Firebug getfirebug.com
• FirePHP firephp.org
The “Pyrotrinity”

87. FirePHP
Takes a moment to set up:

88. FirePHP
Takes a moment to set up:
Use it like this:

89. Today
• Introduction
• Loop basics
• Custom queries
• Method 1: Roll your own query
• Method 2: Filter every query
• Next steps

90. Next steps

91. Next steps
Hit the docs:

92. Next steps
Hit the docs:
• PHP manual: php.net

93. Next steps
Hit the docs:
• PHP manual: php.net
• Codex: codex.wordpress.org

94. Next steps
Hit the docs:
• PHP manual: php.net
• Codex: codex.wordpress.org
• The source:
core.trac.wordpress.org

95. Next steps
Hit the docs:
• PHP manual: php.net
• Codex: codex.wordpress.org
• The source:
core.trac.wordpress.org
• grep it!

96. Next steps

97. Next steps
Learn SQL

98. Next steps
Learn SQL
• The language that WordPress’s raw
database calls are in.

99. Next steps
Learn SQL
• The language that WordPress’s raw
database calls are in.
• It’s really not that scary.

100. Next steps
Learn SQL
• The language that WordPress’s raw
database calls are in.
• It’s really not that scary.
• Lets you write filters directly on
different parts of the query.

101. Next steps
Learn SQL
• The language that WordPress’s raw
database calls are in.
• It’s really not that scary.
• Lets you write filters directly on
different parts of the query.
• EX: mitcho.com/blog/how-to/external-
orders-in-wordpress-queries/

102. Thank you!
Questions?
Slides will be up on mitcho.com/blog/.
See you at the Genius Bar!
mitcho (Michael 芳貴 Erlewine)
mitcho.com; @mitchoyoshitaka