How Not to Build a WordPress Plugin Will Norris < http://willnorris.com />

Will Norris < http://willnorris.com />

Upgradability Performance Security Extensibility

Upgradability

Performance

Security

Extensibility

Unique Function Names

Function Name Prefix wcpdx_activate() wcpdx_deactivate() wcpdx_uninstall()

wcpdx_activate()

wcpdx_deactivate()

wcpdx_uninstall()

Class class WordCampPDX { function activate() function deactivate() function uninstall() }

class WordCampPDX {

function activate()

function deactivate()

function uninstall()

}

Never Assume File Location

Traditional Directory Layout example.com/ wordpress/ wp-config.php wp-content/ plugins/ themes/

example.com/

wordpress/

wp-config.php

wp-content/

plugins/

themes/

Non-Traditional Layout (since WP 2.6) example.com/ wordpress/ wp-config.php wordpress-content/ plugins/ themes/

example.com/

wordpress/

wp-config.php

wordpress-content/

plugins/

themes/

Plugin URL ur doin it wrong: <img src=”<?php bloginfo(‘wpurl’) ?>/wp-content/plugins/wcpdx/logo.png” ?> dats bedder: <img src=”<?php echo WP_PLUGIN_URL ?>/wcpdx/logo.png ?>”/> you haz it: <img src=”<?php echo plugins_url(‘logo.png’, __FILE__) ?>” />

ur doin it wrong:

<img src=”<?php bloginfo(‘wpurl’) ?>/wp-content/plugins/wcpdx/logo.png” ?>

dats bedder:

<img src=”<?php echo WP_PLUGIN_URL ?>/wcpdx/logo.png ?>”/>

you haz it:

<img src=”<?php echo plugins_url(‘logo.png’, __FILE__) ?>” />

Plugin URL plugins_url() supports WPMU plugin directory auto detects SSL supports renamed plugin directory calls ‘plugins_url’ filter

plugins_url()

supports WPMU plugin directory

auto detects SSL

supports renamed plugin directory

calls ‘plugins_url’ filter

Friends of plugins_url() site_url() admin_url() includes_url() content_url() no home_url() (why not?)

site_url()

admin_url()

includes_url()

content_url()

no home_url() (why not?)

Including Files ur doin it wrong: include ‘../../wp-content/...’ dats bedder: include ABSPATH . ‘wp-content/...’ you haz it: include WP_CONTENT_DIR . ‘/...’

ur doin it wrong:

include ‘../../wp-content/...’

dats bedder:

include ABSPATH . ‘wp-content/...’

you haz it:

include WP_CONTENT_DIR . ‘/...’

Find the Right Hook Load as late as possible, but no later

Load as late as possible, but no later

Admin Hooks ur doin it wrong: add_action(‘admin_init’, ‘wcpdx_admin_init’) add_action(‘admin_head’, ‘wcpdx_admin_head’) you haz it: $hookname = add_options_page( ... ) add_action(“admin_load-$hookname”, ‘wcpdx_admin_init’) add_action(“admin_head-$hookname”, ‘wcpdx_admin_head’)

ur doin it wrong:

add_action(‘admin_init’, ‘wcpdx_admin_init’)

add_action(‘admin_head’, ‘wcpdx_admin_head’)

you haz it:

$hookname = add_options_page( ... )

add_action(“admin_load-$hookname”, ‘wcpdx_admin_init’)

add_action(“admin_head-$hookname”, ‘wcpdx_admin_head’)

Styles and Scripts ur doin it wrong: <script rel=”<?php echo plugins_url(‘wcpdx.js’, __FILE__) ?>”></script> you haz it: wp_enqueue_script(‘wcpdx’, plugins_url(‘wcpdx.js’, __FILE__)) wp_enqueue_style(‘wcpdx’, plugins_url(‘wcpdx.css’, __FILE__))

ur doin it wrong:

<script rel=”<?php echo plugins_url(‘wcpdx.js’, __FILE__) ?>”></script>

you haz it:

wp_enqueue_script(‘wcpdx’, plugins_url(‘wcpdx.js’, __FILE__))

wp_enqueue_style(‘wcpdx’, plugins_url(‘wcpdx.css’, __FILE__))

Styles and Scripts wp_register_* and wp_enqueue_* support dependencies push scripts to footer caching support based on version (one day) server side concatenation

wp_register_* and wp_enqueue_*

support dependencies

push scripts to footer

caching support based on version

(one day) server side concatenation

Add your own hooks A strategically placed hook covers a multitude of sins.

A strategically placed hook covers a multitude of sins.

Custom Hooks Can do everything core WP hooks do: event notification (actions) massage data (the_content) replace values (stylesheet) extend functionality (http_api_curl) replace functionality

Can do everything core WP hooks do:

event notification (actions)

massage data (the_content)

replace values (stylesheet)

extend functionality (http_api_curl)

replace functionality

Custom Hooks do_action(‘my-action’) do_action(‘my-action’, $a, $b) do_action_ref_array(‘my-action’, array($wcpdx)) apply_filters(‘my-filter’, $wcpdx) apply_filters(‘my-filter’, $wcpdx, $a, $b)

do_action(‘my-action’)

do_action(‘my-action’, $a, $b)

do_action_ref_array(‘my-action’, array($wcpdx))

apply_filters(‘my-filter’, $wcpdx)

apply_filters(‘my-filter’, $wcpdx, $a, $b)

Custom Tables

Designed for Flexibility WordPress database supports custom options arbitrary metadata for posts, users, and comments (2.9) custom taxonomies custom post types

WordPress database supports

custom options

arbitrary metadata for posts, users, and comments (2.9)

custom taxonomies

custom post types

Custom Post Types Used by WordPress core for posts pages revisions attachments

Used by WordPress core for

posts

pages

revisions

attachments

If it walks like a duck... author date and time title content comments categories and tags permalink order hierarchy (additional arbitrary metadata)

author

date and time

title

content

comments

categories and tags

permalink

order

hierarchy

(additional arbitrary metadata)

Admin Settings Pages

Admin Settings Pages Don’t waste time processing manually register_setting( ‘wcpdx’, ‘my-option’ ) http://codex.wordpress.org/Settings_API http://codex.wordpress.org/Creating_Options_Pages# Register_Settings

Don’t waste time processing manually

register_setting( ‘wcpdx’, ‘my-option’ )

http://codex.wordpress.org/Settings_API

http://codex.wordpress.org/Creating_Options_Pages# Register_Settings

Admin Settings Pages Do you really need a dedicated page? Add options to any built-in settings page add_settings_field( ... )

Do you really need a dedicated page?

Add options to any built-in settings page

add_settings_field( ... )

Direct Plugin Files

Direct Plugin File Calls Direct HTTP request to plugin file ajax.php: echo ‘<script type=”text/javascript”> jQuery.get(“‘ . plugins_url(‘ajax.php’, __FILE__) . ‘”); // do something with AJAX data </script>’;

Direct HTTP request to plugin file ajax.php:

echo ‘<script type=”text/javascript”>

jQuery.get(“‘ . plugins_url(‘ajax.php’, __FILE__) . ‘”);

// do something with AJAX data

</script>’;

Direct Plugin File Calls If ajax.php includes anything similar to: require_once(‘../../../wp-load.php’); ur doin it wrong

If ajax.php includes anything similar to:

require_once(‘../../../wp-load.php’);

ur doin it wrong

WordPress Requests Permalink URL: http://example.com/2009/01/hello-world becomes: http://example.com/index.php? year=2009& monthnum=01& name=hello-world

Permalink URL:

http://example.com/2009/01/hello-world

becomes:

http://example.com/index.php?

year=2009&

monthnum=01&

name=hello-world

Custom WP Request Instead of making an AJAX call to: http://example.com/wp-content/plugins/wcpdx/ajax.php we want a URL like: http://example.com/index.php?wcpdx=ajax-handler

Instead of making an AJAX call to:

http://example.com/wp-content/plugins/wcpdx/ajax.php

we want a URL like:

http://example.com/index.php?wcpdx=ajax-handler

Custom WP Requests function wcpdx_parse_request($wp) { // only process requests with &quot;wcpdx=ajax-handler&quot; if (array_key_exists('wcpdx', $wp->query_vars) && $wp->query_vars['wcpdx'] == 'ajax-handler') { // process the request. } } add_action('parse_request', 'wcpdx_parse_request'); function wcpdx_query_vars($vars) { $vars[] = 'wcpdx'; return $vars; } add_filter('query_vars', 'wcpdx_query_vars');

function wcpdx_parse_request($wp) {

// only process requests with &quot;wcpdx=ajax-handler&quot;

if (array_key_exists('wcpdx', $wp->query_vars)

&& $wp->query_vars['wcpdx'] == 'ajax-handler') {

// process the request.

}

}

add_action('parse_request', 'wcpdx_parse_request');

function wcpdx_query_vars($vars) {

$vars[] = 'wcpdx';

return $vars;

}

add_filter('query_vars', 'wcpdx_query_vars');