Intro to Plugin Development, Miami WordCamp, 2015

Intro To Plugin Development

Emptying out functions.php

Intro To Plugin DevelopmentTopher DeRosia

@topher1kenobe

Hi, my name is TopherI’m a WordPress developer from

Grand Rapids MI

@topher1kenobe


Topher DeRosia@topher1kenobe

“Just put this code in your theme’s functions.php file…”

JUST SAY NO



Plugins are packages of code that affect your site’s functionality.

Themes are packages of code that affect your site’s design.

DO NOT MIX.Intro To Plugin Development


Plugins are either single files or folders in /wp-content/plugins



Typically inside each plugin folder is a file with the same name as the folder, plus any other files it needs.



In the top of every main plugin file is a header block with information about the plugin.



The only option absolutely required is the “Plugin Name”. The others are merely strongly recommended.

VERY strongly recommended:License: GNU General Public License v2 or laterLicense URI: http://www.gnu.org/licenses/gpl-2.0.htmlTags: custom-header, custom-menu, editor-style, featured-images (etc)



http://www.gnu.org/licenses/gpl-2.0.html

The Secret Sauce:

Any code you might have put into functions.php in your theme could go into a plugin.*

*with a few exceptions



Example:

<?php/*Plugin Name: Topher’s Little PluginDescription: Does things I want to my siteVersion: 1.0Author: Topher*/

// 220 pixels wide by 180 pixels tall, hard crop modeadd_image_size( 'custom-size', 220, 180, true );?> Intro To Plugin Development


Longer Example:<?php/*Plugin Name: Topher’s Little PluginDescription: Does things I want to my siteVersion: 1.0Author: Topher*/

// 220 pixels wide by 180 pixels tall, hard crop modeadd_image_size( 'custom-size', 220, 180, true );

// Make shortcodes work inside text widgetsadd_filter('widget_text', 'do_shortcode');

// Fix styling in old contentfunction phlog_scripts() {

wp_enqueue_style( 'phlog_styles', plugins_url( '/css/phlog.css' , __FILE__ ) );}add_action( 'wp_enqueue_scripts', 'phlog_scripts' );

?> Intro To Plugin Development


Explanation:

function phlog_scripts() {wp_enqueue_style( 'phlog_styles', plugins_url( '/css/phlog.css' , __FILE__ ) );

}add_action( 'wp_enqueue_scripts', 'phlog_scripts' );

I made a function called `phlog_scripts()`

Inside it is a function that properly enqueues a CSS file. wp_enqueue_style takes 2 arguments, a name I made up and the path to the CSS file.

The path to the CSS file is determined with the WordPress function plugins_url().



Releasing a Plugin

A plugin built for release on WordPress.org must meet a list of requirements. The requirements are listed at

https://developer.wordpress.org/plugins/wordpress-org/

Best practices are found in the WordPress Plugin Handbook

https://developer.wordpress.org/plugins/



https://developer.wordpress.org/plugins/wordpress-org/


mu-plugins: mu == must usePlugins that are stored in mu-plugins are automatically activated, and cannot be deactivated. The main file of a plugin must be stored directly in the /mu-plugins/ directory, OR be included.



mu-plugins



mu-plugins

To convert a regular plugin to mu-plugins, put it in the /mu-plugins directory and then make a new, single-file plugin that looks like this:

<?php/*Plugin Name: mu-plugins inclusion pluginDescription: Includes the main files of any plugins that are in mu-pluginsAuthor: TopherVersion: 1.0*/

// include widget_logicinclude WP_CONTENT_DIR . '/mu-plugins/widget-logic/widget_logic.php';

?>



Extra Credit: WP-CLI

WP-CLI is the command line tool for WordPress. It can create an empty plugin with the proper header in place:

wp scaffold plugin --prompt

This will ask questions like this:

1/4 <slug>: topher-test2/4 [--plugin_name=<title>]: Topher's Test3/4 [--skip-tests] (Y/n): Y4/4 [--activate] (Y/n): YSuccess: Created /home/topher1/topher1kenobe.com/wp-content/plugins/topher-test1/1 <plugin>: topher-testSuccess: Created test files.



Real World ExampleEasy Digital Downloads - Customer Contact



Easy Digital Downloads - Customer Contact

<?php/*Plugin Name: Easy Digital Downloads - Customer ContactVersion: 1.0Description: Creates a tab on the Customer page for sending an email to that customer.Author: TopherAuthor URI: http://topher1kenobe.comPlugin URI: http://topher1kenobe.comText Domain: edd-customer-contactDomain Path: /languagesLicense: GNU General Public License v2 or laterLicense URI: http://www.gnu.org/licenses/gpl-2.0.html*/




Comment everything!

Docblock/** * Contact a customer * * @since 2.3 * @param array $args The $_POST array being passeed * @return int Whether it was a successful email */

Inline// make sure we're allowed to be here at allif ( ! is_admin() || ! current_user_can( $customer_edit_role ) ) { wp_die( __( 'You do not have permission to contact this customer.', 'edd' ) );} Intro To Plugin Development



Insert Code Review Here




Get Help

From other developers (Slack, Stack Overflow, friends)

From parent plugin developer (if making an Addon they probably want to help)

From documentation (https://developer.wordpress.org/plugins/)

From code (read through plugins doing similar things)




THANKS FOR

LISTENING

Intro To Plugin DevelopmentTopher DeRosia

@topher1kenobe

http://topher1kenobe.comFollow me @topher1kenobe

Internet

Intro to Plugin Development, Miami WordCamp, 2015