Presentation: Plugging Into Wordpress

Plugging intoMatt Harris

<head> conference26th October 2008

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Type

s of

Wor

dpre

ss Wordpress.comHosted blogging solution

Wordpress.orgDownloadable edition for use on your own server

Wordpress MUMulti-user edition of Wordpress.org

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Wor

dpre

ss.c

omHosted

Free

Maintained and backed up for you

Not hackable or pluggable by you

3Hosted: scalable, Automa1c deals with the spikes you may get

Wor

dpre

ss.o

rgCustomisable

Self-hosted

Complete code control

Maintenance, backup and reliability are your responsibility

4Customisable: hackable, expandable. Add your own features

Wor

dpre

ss M

UAll of Wordpress.org pros and cons

Hosting of multiple blogs under one install

Bespoke permission settings per blog

Your own Wordpress.com

5Basically this is the meat behind Wordpress.comGreat for Uni’s, EducaEonal places, newspapers, blog networks etc

User Interface

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User Interface

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User Interface

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User Interface

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Admin Interface

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Admin Interface

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Admin Interface

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Hooks and Filters

add_action($tag, $function, $priority, $accepted_args)

add_filter($tag, $function, $priority, $accepted_args)

http://www.flickr.com/photos/gaetanlee/2906941718/

add_shortcode($tag, $function)

13Don’t hack at the core code – makes it difficult to update the your installaEonUse hooks and filters to ‘inject’ an event into the page processing

Filters are the hooks that WordPress launches to modify text of various types before adding it to the database or sending it to the browser screen

Hooks aOach custom funcEons onto specific acEonshOp://codex.wordpress.org/Plugin_API/AcEon_ReferencehOp://codex.wordpress.org/Plugin_API/Filter_ReferencehOp://codex.wordpress.org/Shortcode_API

Where to put your code

PluginsInside it’s own file

Theme folder in the file

functions.php

14Plugins advantage – easily switch off and onableFuncEons – will always run – best if required as part of your theme (not covered today but example would be to change something a theme relies on – maybe the movement of a login buOon)

Simple Filter

<?php

function changeWord($content) { $search = “wordpress”; $replace = “my blog”; return str_ireplace($search, $replace, $content);}

add_filter(‘the_content’, ‘changeWord’);

?>

http://codex.wordpress.org/Plugin_API/Filter_Reference

15‘the_content” is a built in Wordpress tagStr_ireplace is case insensiEve

To test this included it in funcEons.php

Simple Filter

<?php

function changeWord($content) { $search = “wordpress”; $replace = “my blog”; return str_ireplace($search, $replace, $content);}

add_filter(‘the_content’, ‘changeWord’);

?>

http://codex.wordpress.org/Plugin_API/Filter_Reference

16‘the_content” is a built in Wordpress tagStr_ireplace is case insensiEve

To test this included it in funcEons.php

Simple Filter

Before After

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Simple Hook

<?php

function addText() { echo “Can you see me?”;}

add_action(’wp_footer', ’addText’);

?>

http://codex.wordpress.org/Plugin_API/Action_Reference

18wp_footer Runs when the template calls the wp_footer funcEon, generally near the boOom of the blog page.

Simple Hook

<?php



?>



Simple Hook<?php

function changeTextCol() { echo “ <style type=‘text/css’> body { color: #0ff00f; } </style> “;}

add_action(’wp_head', ’changeTextCol’);

?>



Simple Hook

Before After

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Simple Shortcode<?php

function myH1_shortcode($atts, $content = null) { extract($atts); return ‘ <div class=“heading”> <h1 style=“color:’ . $colour . ‘”>' . $content . '</h1> </div>’;}

add_shortcode(’heading', 'myH1_shortcode');

?>

http://codex.wordpress.org/Shortcode_API

22Shortcodes cannot be nested be default. Must add do_shortcode($content) into your handler to do this

Since WP2.5 (fixed 2.5.1. parsing order)

Note this isn’t really safe, $content should be saniEzed first using (stripslashes(wp_filter_post_kses($content) and colour should be protected with aOribute_escape($colour)

Simple Shortcode<?php

[heading color=“#f00”]This is my heading[/heading]

?>

Output

<div class="heading"> <h1 style="color:#f00">This is my heading</h1></div>

23Shortcodes cannot be nested be default. Must add do_shortcode($content) into your handler to do this

Namespacing

http://www.flickr.com/photos/thost/2244046981/24

Namespacing

<?php



?>

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Namespacing

<?php

function tmh_addText() { echo “Can you see me?”;}

add_action(’wp_footer', ’tmh_addText’);

?>

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Widgets

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Plugin Code Structure<?php

/*Plugin Name: My WidgetPlugin URI: http://themattharris.comDescription: A widget that puts some text in the sidebarAuthor: Matt HarrisVersion: 1.0Author URI: http://themattharris.com*/

?>

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Widget Code Structure<?php

function tmh_renderWidget($args) { extract($args); ?> <?php echo $before_widget; ?> <?php echo $before_title . wptexturize(’My Widget') . $after_title; ?> <p>My Widget Code</p> <?php echo $after_widget; ?> <?php}

?>

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?>

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?>

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function tmh_renderWidget($args) { extract($args); ?> <?php echo $before_widget; ?> <?php echo $before_title . wptexturize(‘My Widget’) . $after_title; ?> <p>My Widget Code</p> <?php echo $after_widget; ?> <?php}

?>

32wp_specialchars ‐ Like htmlspecialchars except don't double‐encode HTML enEEes

<?php


?>

Widget Code Structure

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Widget Registration Code<?php

function tmh_widgetInit() { if (function_exists('register_sidebar_widget’)) { register_sidebar_widget('My Widget', 'tmh_renderWidget'); }}

add_action( 'widgets_init', 'tmh_widgetInit');

?>

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Putting it all together<?php/*Plugin Name: My WidgetPlugin URI: http://themattharris.comDescription: A widget that puts some text in the sidebarAuthor: Matt HarrisVersion: 1.0Author URI: http://themattharris.com*/

function tmh_renderWidget($args) { extract($args); ?> <?php echo $before_widget; ?> <?php echo $before_title . wptexturize('My Widget') . $after_title; ?>

<p>My Widget Code</p>

<?php echo $after_widget; ?> <?php}

function tmh_widgetInit() { if ( function_exists('register_sidebar_widget') ) { register_sidebar_widget('My Widget', 'tmh_renderWidget'); }}

add_action( 'widgets_init', 'tmh_widgetInit');

?>

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Making it work

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Making it work

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Making it work

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Making it work

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Protecting your blog

check_admin_referer($action, [$query_arg]);

Use with

wp_create_nonce($action);

Use this on any forms you have.

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attribute_escape($text); // also tag escape

wp_filter_post_kses($data); // adds slashes

wp_filter_nohtml_kses($data); // adds slashes

Use these when outputting data

43aOribute_escape (used for escaping for HTML aOributes)

Kses checks for allow html (or removes it in nohtml)


<?php current_user_can($capability) ?>

http://codex.wordpress.org/Roles_and_Capabilities

<?php if (current_user_can(‘unfiltered_html’)) { $data = Wp_filter_post_kses($data); } else { $data = wp_filter_nohtml_kses($data); }?>

Example

44aOribute_escape (used for escaping for HTML aOributes)

Kses checks for allow html (or removes it in nohtml)

Translation friendly

http://codex.wordpress.org/Translating_WordPress

<?php __($message, $domain); ?>

<?php _e($message, $domain); ?>

<?php _e(“Title:”,’tmh_pluginname’); ?>

Example

45WP uses GNU geOext localizaEon framework

Message level translaEon

_e echos

__ doesn’t

Too much info to go into here on how to have wordpress do the translaEon, but its worth building this in from the start

$message is output/returned if no translaEon is found so always worth building this in

Help and More InformationWordpress Mailing Lists

http://codex.wordpress.org/Mailing_Lists

Wordpress Codex (or Google term + “codex”)

http://codex.wordpress.org/

Wordpress Support Forum

http://wordpress.org/support/

Writing a Plugin

http://codex.wordpress.org/Writing_a_Plugin

46Wordpres support forum – if the FAQ can’t helpGoogle search – whole community out there that can help

Matt Harrishttp://[email protected]

All the links: http://ma.gnolia.com/people/themattharris/tags/plugging%20into%20wordpress

Image credits:“Hello … my name is”: http://www.flickr.com/photos/thost/2244046981/“Hooks for hand”: http://www.flickr.com/photos/gaetanlee/2906941718/“Wordpress Logo”: http://wordpress.org/about/logos/

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Technology

Presentation: Plugging Into Wordpress