Wordpress Meetup 2 23 10
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Wordpress Meetup 2 23 10



Writing your first WordPress plugin

Writing your first WordPress plugin



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Wordpress Meetup 2 23 10 Wordpress Meetup 2 23 10 Presentation Transcript

  • Writing Your First WordPress Plugin or, What I wish someone had told me because it would have prevented me from banging my head on the desk a lot Boone Gorges @boonebgorges [email_address] http://teleogistic.net
  • Who am I? – early 2009
    • Instructional Technologist, Queens College, CUNY
    • Philosopher
    • Good HTML and CSS knowledge. Some scripting experience
    • Moderately high awesomeness
  • Who am I? – early 2010
    • Developer, CUNY Academic Commons http://commons.gc.cuny.edu
    • A zillion plugins in WP repo http://wordpress.org/extend/plugins/profile/boonebgorges
    • Extreme awesomeness
  • 1) The structure of WordPress
  • WordPress is modular Separable pieces: classes, functions, template files Serial: Everything happens in a certain order
  • WordPress is modular Plugins : New classes, functions, or template files that either replace or augment WP “core”
  • 2) Plugin basics
  • Where do plugins live?
    • Ask yourself:
    • Is my plugin specific to a theme?
      • wp-content/[theme-dir]/functions.php
    • Should my plugin activate on all blogs? (MU only)
      • wp-content/mu-plugins/my-plugin.php
    • Otherwise
      • wp-content/plugins/my-plugin/my-plugin.php
  • Let WP know you exist <?php /* Plugin Name: Boone’s Plugin Plugin URI: http://teleogistic.net Description: This plugin will blow your mind Author: boonebgorges Version: 1.0 Author URI: http://teleogistic.net */ wp-content/plugins/boones-plugin/boones-plugin.php See http://codex.wordpress.org/Writing_a_Plugin#File_Headers
  • 3) Example: Shortcode
  • Shortcodes fill in for frequently-typed stuff Say you typed your address a lot:
  • The WordPress Shortcode API function address_shortcode() { return '<p>Boone Gorges<br /> 24 Gumdrop Lane<br /> Apartment #32<br /> Sugarlove, MD 20020</p>'; } add_shortcode( 'bgaddress', 'address_shortcode' ); wp-content/plugins/boones-plugin/boones-plugin.php See http://codex.wordpress.org/Shortcode_API
  • Soup that baby up function address_shortcode($atts) { extract(shortcode_atts(array( 'location' => 'MD' ), $atts)); if ( $atts['location'] == 'MD' ) return '<p>Boone Gorges<br /> 24 Gumdrop Lane<br /> Apartment #32<br /> Sugarlove, MD 20020</p>'; else return '<p>Boone Gorges<br /> 85 Lollipop Street<br /> Apartment #81<br /> Milwaukee, WI 54112</p>'; } add_shortcode( 'bgaddress', 'address_shortcode' ); wp-content/plugins/boones-plugin/boones-plugin.php See http://codex.wordpress.org/Shortcode_API
  • There's a Widgets API too See http://codex.wordpress.org/Widgets_API
  • 4) Example: Hooks
  • Actions are hooks In the core: do_action( 'loop_start' ); In your plugin: add_action( 'loop_start', 'my_code' );
  • Example: A hello message function well_hello_there() { global $user_identity; if ( is_user_logged_in() ) echo &quot;Welcome, &quot; . $user_identity; else echo &quot;Welcome, anonymous lurker!&quot;; } add_action( 'loop_start', 'well_hello_there' ); wp-content/plugins/boones-plugin/boones-plugin.php See http://codex.wordpress.org/Plugin_API/Action_Reference
  • Filters are hooks… with benefits In the core: $content = apply_filters('the_content', $content); In your plugin: add_filter( 'the_content', 'my_code' );
  • Example: Makin' it 1337 function make_it_leet( $content ) { $leet_content = str_replace( 'e', '3', $content ); return $leet_content; } add_filter( 'the_content', 'make_it_leet' ); wp-content/plugins/boones-plugin/boones-plugin.php See http://codex.wordpress.org/Plugin_API/Filter_Reference
  • 5) The plugin dev's toolbox
  • Resources on the web The WordPress Codex, especially: - http://codex.wordpress.org/Shortcode_API - http://codex.wordpress.org/Widgets_API - http://codex.wordpress.org/Plugin_API The WordPress PHP Cross-Reference - http://xref.yoast.com The WordPress plugin repository: - http://wordpress.org/extend/plugins to download - http://wordpress.org/extend/plugins/about to add your own plugin PHP resources - W3Schools – http://www.w3schools.com/PHP/ - php.net – http://www.php.net/manual/en
  • Resources on your computer A good text editor, ideally one with - the ability to save over FTP - good search-and-replace - code highlighting - see http://lifehacker.com/385929/best-text-editors for suggestions A local development environment - AMP: Apache, MySQL, PHP - Windows: XAMPP; Mac: MAMP - Use SVN to get the most recent copies of WordPress
  • Words of advice The White Screen Of Death - Usually means you have a syntax error (check your punctuation!) - No duplicate function names, except for functions in pluggable.php - Use if ( function_exists( 'my_function' ) ) Get to know your data - Learn about globals: $wp, $post, $comment - var_dump( $wp ); - print &quot;<pre>&quot;; print_r( $wp ); print &quot;</pre>&quot;; - die(); Pick apart existing plugins Ask for help: http://wordpress.org/support
  • Booyah! Boone Gorges @boonebgorges [email_address] http://teleogistic.net