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Presented at the Boston WordPress meetup, September 28, 2009."In this presentation I will give a high level overview of how WordPress can be customized through custom plugins. I will walk through the creation of a very simple plugin in PHP, the default development language for WordPress. I will then present HookPress (http://mitcho.com/code/hookpress/) which is a plugin of mine which adds webhooks to WordPress, letting developers extend WordPress in languages other than PHP, such as ruby, python, perl, etc.""This will be an intermediate level session designed for users already comfortable with publishing with and customizing a wordpress.org installation and have maybe even installed a few plugins. Moreover, I will assume some familiarity with programming, though not necessarily the PHP language."
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Extending WordPress with (Web)Hooks
mitcho (Michael 芳貴 Erlewine)http://mitcho.com
September 28, 2009Boston WordPress Meetup
Today• Introduction• Modifying WordPress behavior• filters and actions
• Writing our first plugin in PHP• Extending WordPress with webhooks via HookPress
Today
NOTE:• Will link to slides and code later on Meetup site
• Please rate later on SpeakerRate• again, link on Meetup.com
Today• Introduction• Modifying WordPress behavior• filters and actions
• Writing our first plugin in PHP• Extending WordPress with webhooks via HookPress
Introduction
Introduction• Hi, I’m mitcho.
Introduction• Hi, I’m mitcho.• Linguist, coder, teacher.
Introduction• Hi, I’m mitcho.• Linguist, coder, teacher.
• At MIT. Previously at Mozilla.
Introduction• Hi, I’m mitcho.• Linguist, coder, teacher.
• At MIT. Previously at Mozilla.• Programming PHP/MySQL since 2002?
Introduction• Hi, I’m mitcho.• Linguist, coder, teacher.
• At MIT. Previously at Mozilla.• Programming PHP/MySQL since 2002?• Blogging (off and on) at mitcho.com since 2007.
Introduction• Hi, I’m mitcho.• Linguist, coder, teacher.
• At MIT. Previously at Mozilla.• Programming PHP/MySQL since 2002?• Blogging (off and on) at mitcho.com since 2007.
• http://mitcho.com; @mitchoyoshitaka
Introduction
Introduction
• Yet Another Related Posts Plugin
Introduction
• Yet Another Related Posts Plugin• ...aka YARPP
Introduction
• Yet Another Related Posts Plugin• ...aka YARPP• As seen on Laughing Squid, ma.tt...
Introduction
• Yet Another Related Posts Plugin• ...aka YARPP• As seen on Laughing Squid, ma.tt...• Over 250k downloads
Introduction
• Yet Another Related Posts Plugin• ...aka YARPP• As seen on Laughing Squid, ma.tt...• Over 250k downloads
• http://mitcho.com/code/yarpp or search for “YARPP”; @yarpp
Today• Introduction• Modifying WordPress behavior• filters and actions
• Writing our first plugin in PHP• Extending WordPress with webhooks via HookPress
WordPress
WordPress
• Open-source, http://wordpress.org• PHP/MySQL• Today: not wordpress.com
WordPress
WordPress
• Self-hosted, so in theory you could modify it it directly
WordPress
• Self-hosted, so in theory you could modify it it directly• Not recommended!
WordPress
• Self-hosted, so in theory you could modify it it directly• Not recommended!
• Highly extensible plugin architecture
WordPress
• Self-hosted, so in theory you could modify it it directly• Not recommended!
• Highly extensible plugin architecture• WordPress itself uses it to modify its own behavior
Modifying behavior
Modifying behavior
• How does WordPress work?
Modifying behavior
• How does WordPress work?• Example: displaying a post’s content
Modifying behavior
• How does WordPress work?• Example: displaying a post’s content
parse URL
Modifying behavior
• How does WordPress work?• Example: displaying a post’s content
parse URL get content from db
Modifying behavior
• How does WordPress work?• Example: displaying a post’s content
parse URL get content from db display
Modifying behavior
• How does WordPress work?• Example: displaying a post’s content
parse URL get content from db display
• but it’s not actually that simple
Modifying behavior
• How does WordPress work?• Example: displaying a post’s content
parse URL get content from db display
• but it’s not actually that simple
smart quotes, paragraph splitting, HTML formatting, smilies...
get content from db display
Modifying behavior
get content from db display
I have the content and am about to display it. Who wants to modify it first?
Modifying behavior
get content from db display
I have the content and am about to display it. Who wants to modify it first?
wp_texturize
convert_smilies
wpautop
...
Modifying behavior
get content from db display
I have the content and am about to display it. Who wants to modify it first?
wp_texturize
convert_smilies
wpautop
...
Modifying behavior
get content from db display
I have the content and am about to display it. Who wants to modify it first?
wp_texturize
convert_smilies
wpautop
...
Modifying behavior
get content from db display
I have the content and am about to display it. Who wants to modify it first?
wp_texturize
convert_smilies
wpautop
...
Modifying behavior
get content from db display
I have the content and am about to display it. Who wants to modify it first?
wp_texturize
convert_smilies
wpautop
...
Modifying behavior
get content from db display
I have the content and am about to display it. Who wants to modify it first?
wp_texturize
convert_smilies
wpautop
...
Modifying behavior
get content from db display
I have the content and am about to display it. Who wants to modify it first?
wp_texturize
convert_smilies
wpautop
...
Modifying behavior
Your customfunctions here:
get content from db display
I have the content and am about to display it. Who wants to modify it first?
wp_texturize
convert_smilies
wpautop
...
Modifying behavior
get content from db display
I have the content and am about to display it. Who wants to modify it first?
wp_texturize
convert_smilies
wpautop
...
Modifying behavior
get content from db display
I have the content and am about to display it. Who wants to modify it first?
wp_texturize
convert_smilies
wpautop
...
Modifying behavior
This is a filter pattern:multiple functions act asfilters on the same text/target.
get content from db display
I have the content and am about to display it. Who wants to modify it first?
Modifying behavior
get content from db display
I have the content and am about to display it. Who wants to modify it first?
Modifying behavior
Each such filter hook (= “pathway,” “process”) has a name. This one is called the_content.
Modifying behavior
Modifying behavior
• Every filter function must be registered against that filter hook ahead of time:
Modifying behavior
• Every filter function must be registered against that filter hook ahead of time:
add_filter(“the_content”, “my_function_name”);
Modifying behavior
• Every filter function must be registered against that filter hook ahead of time:
add_filter(“the_content”, “my_function_name”);
hook name
Modifying behavior
• Every filter function must be registered against that filter hook ahead of time:
add_filter(“the_content”, “my_function_name”);
hook name function name
Modifying behavior
Modifying behavior
• There’s another kind of hook:
Modifying behavior
• There’s another kind of hook:• actions
Modifying behavior
• There’s another kind of hook:• actions• target certain “events” that occur.
Modifying behavior
• There’s another kind of hook:• actions• target certain “events” that occur.• Examples: a post is published, a comment is made, someone accesses wp-admin, etc.
Modifying behavior
Modifying behavior
• actions...
Modifying behavior
• actions...• don’t necessarily modify anything but can trigger other processes.
Modifying behavior
• actions...• don’t necessarily modify anything but can trigger other processes.
• can also produce output, modify the database, etc.
Modifying behavior
Modifying behavior
• filters...
Modifying behavior
• filters...• modify (filter) something and return it.
Modifying behavior
• filters...• modify (filter) something and return it.
• The return value matters.
Modifying behavior
• filters...• modify (filter) something and return it.
• The return value matters.• actions...
Modifying behavior
• filters...• modify (filter) something and return it.
• The return value matters.• actions...• correspond to an “event.”
Modifying behavior
• filters...• modify (filter) something and return it.
• The return value matters.• actions...• correspond to an “event.”• Return values don’t matter.
Today• Introduction• Modifying WordPress behavior• filters and actions
• Writing our first plugin in PHP• Extending WordPress with webhooks via HookPress
Today
TodayNOTE:
TodayNOTE:• I’m using MAMP: Mac, Apache, MySQL, PHP.
TodayNOTE:• I’m using MAMP: Mac, Apache, MySQL, PHP.• Similar to XAMPP on Windows.
TodayNOTE:• I’m using MAMP: Mac, Apache, MySQL, PHP.• Similar to XAMPP on Windows.• Working on a server directly is okay too...
TodayNOTE:• I’m using MAMP: Mac, Apache, MySQL, PHP.• Similar to XAMPP on Windows.• Working on a server directly is okay too...• but avoid working on live sites.
Writing a plugin
Task: display a word count for posts
Writing a plugin
Writing a plugin
Writing a plugin
• PHP script
Writing a plugin
• PHP script• Place in wp-content/plugins/
Writing a plugin
• PHP script• Place in wp-content/plugins/• Requires a certain header
http://codex.wordpress.org/Writing_a_Plugin
Writing a plugin
The plan:1.Write a filter function which...a. takes the content as its input;b. counts the words;c. adds, for ex., <p>(43 words)</p> to the end of the content;
d. returns the modified content;
Writing a plugin
The plan:1.Write a filter function which...2.Register that function as a filter. Use the the_content filter hook.
Writing a plugin
Task (continued): add a sponsorship message
Writing a plugin
Writing a plugin
The plan (continued):3.Write an action function which prints the message.
4.Register it against the wp_footer action hook.
Note:
Note:
This is a filter...
Note:
This is a filter...
...so it takes an argument...
Note:
This is a filter...
...so it takes an argument...
...and returns it after modifying.
Note:
Note:
This is an action...
Note:
This is an action...
...so it returns nothing.
Writing a plugin
Writing a plugin
• Right now the counting happens on the archive and front pages as well.
Writing a plugin
• Right now the counting happens on the archive and front pages as well.
• Use the WordPress is_single() conditional tag.
Writing a plugin
• Right now the counting happens on the archive and front pages as well.
• Use the WordPress is_single() conditional tag.• You may have seen such conditional tags in theme development.
Resources
Resources
• PHP manual: php.net• Codex: codex.wordpress.org/Writing_a_Plugin and links there
Resources
• PHP manual: php.net• Codex: codex.wordpress.org/Writing_a_Plugin and links there
• Forum: wordpress.org/support/forum/10
Resources
• PHP manual: php.net• Codex: codex.wordpress.org/Writing_a_Plugin and links there
• Forum: wordpress.org/support/forum/10• The source: core.trac.wordpress.org/
Look into...
Look into...
• Namespacing: use function_exists(), classes, unique names.
Look into...
• Namespacing: use function_exists(), classes, unique names.
• Saving options: get_option(), etc.
Look into...
• Namespacing: use function_exists(), classes, unique names.
• Saving options: get_option(), etc.• Adding an options screen: codex.wordpress.org/Adding_Administration_Menus
Look into...
Look into...
• Security: use data validation for HTML, SQL queries, etc.
Look into...
• Security: use data validation for HTML, SQL queries, etc.• WordPress helps you: codex.wordpress.org/Data_Validation
Look into...
• Security: use data validation for HTML, SQL queries, etc.• WordPress helps you: codex.wordpress.org/Data_Validation
• Share! Consider uploading to wordpress.org/extend
Today• Introduction• Modifying WordPress behavior• filters and actions
• Writing our first plugin in PHP• Extending WordPress with webhooks via HookPress
Extending WordPress
Extending WordPress
PHP
Extending WordPress
• What if...
PHP
Extending WordPress
• What if...• you’re more comfortable in another language?
PHP
Extending WordPress
• What if...• you’re more comfortable in another language?
• you want to integrate WordPress with another system?
PHP
WordPress
+ HookPressWordPress
+ HookPressWordPress
+ HookPressWordPress
action!filter!
+ HookPressWordPress
action!filter!
+ HookPressWordPress
action!filter! your
script
local or remote
+ HookPressWordPress
action!filter! your
script
local or remote
+ HookPressWordPress
action!filter! POST your
script
local or remote
WordPress + HookPress
• create POST webhooks
WordPress + HookPress
• create POST webhooks• supports both actions...
WordPress + HookPress
• create POST webhooks• supports both actions...• create push notifications
WordPress + HookPress
• create POST webhooks• supports both actions...• create push notifications
• ...and filters
WordPress + HookPress
• create POST webhooks• supports both actions...• create push notifications
• ...and filters• extend WordPress without PHP
WordPress + HookPress
Get HookPress
• mitcho.com/code/hookpress• Screencast online
• Stay in touch!• @hookpress on twitter
Get HookPress
Resources
• Check the HookPress request:
Resources
• Check the HookPress request:• postbin.org
• Run basic/proxy scripts:
Resources
• Check the HookPress request:• postbin.org
• Run basic/proxy scripts:• scriptlets.org
Resources
• Check the HookPress request:• postbin.org
• Run basic/proxy scripts:• scriptlets.org
• General WebHooks information:
Resources
• Check the HookPress request:• postbin.org
• Run basic/proxy scripts:• scriptlets.org
• General WebHooks information:• webhooks.org
Resources
Thank you!Questions?
Please rate the talk on SpeakerRate.
mitcho (Michael 芳貴 Erlewine)mitcho.com; @mitchoyoshitaka
