Best practices for WordPress plugin development

Slides for the first part of this tutorial presented on October 4th 2013 at PHPNW, Manchester, UK.
http://conference.phpnw.org.uk/phpnw13/
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With the release of WP3, WordPress has become a serious contender on the CMS market. The WordPress plugin system allows you to add functionality to WordPress in a snap and turn it into much more than ‘just a blogging platform’.
Learn how to develop for WordPress like a pro and take WordPress to the next level.
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Tutorial code:
https://github.com/jrfnl/wp-plugin-best-practices-demo

Transcript

1. Best practices for WordPress plugin development Tutorial @ PHPNW2013 Juliette Reinders Folmer
2. Juliette Reinders Folmer Email: juliette@adviesenzo.nl Web: http://www.adviesenzo.nl/ LinkedIn: http://nl.linkedin.com/in/julietterf Twitter: http://twitter.com/jrf_nl GitHub: http://github.com/jrfnl/ WordPress: http://profiles.wordpress.org/jrf
7. Anatomy of WP Core Plugins Themes Languages Js Libraries Post Types Taxonomies Content areas: Front-end: Header Main (Loop) Sidebar (Widgets) Footer Back-end: Admin Bar Menu Post Types Metaboxes Settings pages
9. Hooks Actions – do something Filters – filter someting and return the result See: Manual Hooks database: http://adambrown.info/p/wp_hooks Debug Bar - Action& filter hooks plugin
11. The Loop <?php if ( have_posts() ) { while ( have_posts() ) { the_post(); // // Post Content here // } // end while } // end if ?>
13. Don’t reinvent the wheel Dashboard Widgets API Database API HTTP API File Header API Filesystem API Heartbeat API Metadata API Options API Plugin API Quicktags API Rewrite API Settings API Shortcode API Theme modification API Theme customization API Transients API Widgets API XML-RPC WordPress API
15. Avoid conflict function_exists() class_exists() Jquery no conflicts mode Use bundled libraries
17. Be Unique PHP: Classes Functions global vars (global) constants WP: shortcodes option(s) / meta fields nonces settings pages custom post types hooks Filenames HTML/CSS: classes, ids Javascript: I18n object functions Multi-lingual I18n text domain Choose your plugin name carefully & implement consistently
19. Be lazy, be lean Use the available is_...() functions Conditional loading of include files Conditional loading of css / js both on admin as well as frontend! Minify js and css New in WP3.6: has_shortcode()
21. Be safe Check early & check often Validation all input sanitize_text_field(), sanitize_title(), sanitize_meta() etc function group Escape all output esc_html(), esc_attr(), esc_url(), esc_textarea(), esc_js() etc Use wp_nonce
23. Be worldly GetText UTF-8 Impact on data validation
26. Don’t get discouraged WP_DEBUG constants Enable error logging! wp_config.php: @ini_set() set_error_handling() to a backtrace function Debug bar to the rescue JS console logging + plugin set_transient() Beware: Lots of templates which do not comply to the WP standards!
31. Starting a plugin <?php /* Plugin Name: Demo Quotes Plugin Plugin URI: https://github.com/jrfnl/wp-plugin-best- practices-demo Description: Demo plugin for WordPress Plugins Best Practices Tutorial Version: 1.0 Author: Juliette Reinders Folmer Author URI: http://adviesenzo.nl/ Text Domain: demo-quotes-plugin Domain Path: /languages/ License: GPL v3 */
32. What every plugin needs Hook your functionality onto actions and filters Loading your localization files Load CSS Load JS Do something Add admin page or add to another admin page Help information Activation/ Upgrade routines Uninstall routines ...
34. Hooks Offer your own action hooks Offer your own filter hooks Document using the @api tag
36. To sum up: Use classes, class constants and statics Most plugins run as singletons Leave as small a footprint in the global namespace as possible Prefix ALL your css classes/ids, js functions and anything else in the global namespace Use WP functions – combined knowledge of thousands
37. Credits Anatomy - Eva di Martino http://www.pureblacklove.com Bridge - Glenn Euloth http://www.flickr.com/photos/eulothg/4956082108/ Conflict - Asaf Antman http://www.flickr.com/photos/asafantman/5134136997/ Help - Green Kozi http://www.flickr.com/photos/themacinator/3445776069/ Hooks - Raul Lieberwirth http://www.flickr.com/photos/lanier67/185311136/ Hooks – Macroman (red background) http://www.flickr.com/photos/macroman/34644959/ Alone – Jon http://www.flickr.com/photos/jb-london/3594171841/ Fun - Justin Beckley http://www.flickr.com/photos/justinbeckleyphotography/8452437969/ Lazy - Kevin Cauchi http://www.flickr.com/photos/kpcauchi/5376768095/ Loop - Gabe Kinsman http://www.flickr.com/photos/auguris/5286612308/ Security – kismihok http://www.flickr.com/photos/kismihok/9686252463/
38. Credits Unique - Luca Volpi (leafs) http://www.flickr.com/photos/luca_volpi/2974346674/ Unique - David Sprinks (birds) http://www.flickr.com/photos/davidspinks/4211976336/ Wheel - Pauline Mak http://www.flickr.com/photos/__my__photos/5025541044/ WordPress - mkhmarketing (crayons) http://www.flickr.com/photos/mkhmarketing/8469030267/ WordPress - Tom Woodward (revolution) http://www.flickr.com/photos/bionicteaching/3048825267/ WordPress - Saad Irfan (core, plugins, themes) http://www.flickr.com/photos/saadirfan/5722057280/ CMS Landscape - Philippe Martin http://www.flickr.com/photos/lafabriquedeblogs/5997969999/ World - Kenneth Lu http://www.flickr.com/photos/toasty/1540997910/ Bike - Pauline Mak http://www.flickr.com/photos/__my__photos/6399028713/ Daisies - Steve Wall http://www.flickr.com/photos/stevewall/4780035332/
39. Keep in touch! (I’m self-employed, you can hire me ;-) ) Juliette Reinders Folmer Email: juliette@adviesenzo.nl Web: http://www.adviesenzo.nl/ LinkedIn: http://nl.linkedin.com/in/julietterf Twitter: http://twitter.com/jrf_nl GitHub: http://github.com/jrfnl/ WordPress: http://profiles.wordpress.org/jrf Please rate this talk on joined.in/ Endorsements and recommendations on LinkedIn are much appreciated too!