1.
@ylefebvre
ylefebvre.ca
Plugins
A Double-Edged Sword
Yannick Lefebvre
Plugin Developer
Presentation available at:
yannickcorner.nayanna.biz/wcmtl2013

2.
@ylefebvre
ylefebvre.ca
Plugins: A Double-Edged Sword
● About me
● The power of plugins
● The wild nature of plugins
● Site-building strategies
● Troubleshooting plugin issues
● Handling problematic updates
● Avoiding bad plugin breakups
● Conclusions

3.
@ylefebvre
ylefebvre.ca
About ME
● Using WordPress since 2004
● Released first plugin (Link Library) in 2005
● Released 8 Plugins on the official repository

4.
@ylefebvre
ylefebvre.ca
The Power of Plugins
● Custom code modules that can be
downloaded and added to WordPress
● Can change almost any aspect of
WordPress
– Add extra content / new functionality
– Modify / enhance default behavior
– Simplify complex tasks

5.
@ylefebvre
ylefebvre.ca
The Power of Plugins
● Allow integrators to create custom content
without modifying core
● Large developer community
● More than 25 000 plugins available, plus
premium plugins!

6.
@ylefebvre
ylefebvre.ca
The Wild Nature of Plugins
● Only available on self-hosted installs
● No enforced coding standard
● Difficult to assess performance and quality
● No code reviews
● No easy way to identify bad updates
● Difficult to predict interaction with site and
other plugins

7.
@ylefebvre
ylefebvre.ca
Building a site with plugins...
...can feel A BIT UNSTABLE

8.
@ylefebvre
ylefebvre.ca
Site-building strategies
● Perform due diligence on a
plugin
– Version compatibility
– Number of downloads
– Positive / Negative ratings
– Number of resolved support
threads

9.
@ylefebvre
ylefebvre.ca
Site-building strategies
● Assess plugin functionality through docs
and examples
● Create a development site to test before
deployment
● Only add one plugin at a time

10.
@ylefebvre
ylefebvre.ca
Site-building strategies
● Measure site performance before and after
plugin installation
– Front-end and admin pages
– Log out to see regular visitors performance

11.
@ylefebvre
ylefebvre.ca
Troubleshooting plugin issues
● Deactivate the last plugin installed
● Deactivate all other plugins and bring back
one at a time to identify source of conflict
● Visit the official plugin page
– Installation procedure
– FAQ
– Support Forum
● Contact the plugin author

12.
@ylefebvre
ylefebvre.ca
TROUBLESHOOTING Styling issues
● Many plugins render content on site pages
● Usually provide their own styling for this
content
● Stylesheets don't always like to agree with
each other

13.
@ylefebvre
ylefebvre.ca
TROUBLESHOOTING Styling issues

14.
@ylefebvre
ylefebvre.ca
TROUBLESHOOTING Styling issues
● Theme can be modified
– Users don't always know full impact of changes
● Plugin stylesheet can be modified
– Avoid changing plugin files (Plugin updates
override file changes)
– Backup files if no other option
– Some plugins have stylesheet editors
– The !important CSS keyword is very useful

15.
@ylefebvre
ylefebvre.ca
Troubleshooting jQuery issues
● Most animated / dynamic site elements
today are powered by jQuery
● jQuery conflicts can easily occur when a
theme and one or more plugins are mixed
● A conflict usually breaks all jQuery elements
on a site

16.
@ylefebvre
ylefebvre.ca
● FireBug (getfirebug.com) is the perfect tool
to identify jQuery / javascript conflicts
Troubleshooting jQuery issues

17.
@ylefebvre
ylefebvre.ca
TYPICAL JQUERY ISSUES
● More than one copy of jQuery.js is loaded
– Verify in page source code
– Each additional copy wipes out previous work
● An incompatible version of jQuery is loaded
– E.g. Google API version loaded for speed boost

18.
@ylefebvre
ylefebvre.ca
TYPICAL JQUERY ISSUES
● Multiple versions of javascript/jQuery
library are loaded by different plugins
● Theme or plugin jQuery code uses
unavailable jQuery shorthand
– All jQuery calls should use jQuery long-form
instead of $ or re-create the shorthand
themselves

19.
@ylefebvre
ylefebvre.ca
Troubleshooting jQuery issues
● In the previous example, two plugins were
loading different versions of the same
jQuery library

20.
@ylefebvre
ylefebvre.ca
Troubleshooting upload issues
● Lack of permissions
– Increase write permissions on upload folder
● Exceeding server maximum upload file size
– Not controlled by WordPress
– Set in server php.ini file (default often 8 MB)
– Plugins can display current settings (e.g.
WordPress phpinfo)
– See with hosting company to change settings

21.
@ylefebvre
ylefebvre.ca
Troubleshooting upload issues

22.
@ylefebvre
ylefebvre.ca
Handling problematic updates
● After updating a plugin
– Your entire site stopped working
– All of your javascript-based code stopped
working
– The plugin's expected output no longer works

23.
@ylefebvre
ylefebvre.ca

24.
@ylefebvre
ylefebvre.ca
● Deactivate and reactivate updated plugin(s)
– Ensures that activation routines are executed
(e.g. Database updates, creation of new option
default values)
– Essential when uploading plugins via FTP
– Plugin reboot
Handling problematic updates

25.
@ylefebvre
ylefebvre.ca
Handling problematic updates
● Identify the problematic plugin through
error messages (often contain plugin path)
● Revert to the plugin's previous version from
your most recent site backup

26.
@ylefebvre
ylefebvre.ca
Handling problematic updates
● Check for previous versions

27.
@ylefebvre
ylefebvre.ca
Handling problematic updates
● Not all plugins list previous versions

28.
@ylefebvre
ylefebvre.ca
FIND previous PLUGIN versions
● Trac is a web-based interface for the
Subversion system where all WordPress.org
plugins are stored

29.
@ylefebvre
ylefebvre.ca
FIND previous PLUGIN versions
Current plugin version is usually trunk

30.
@ylefebvre
ylefebvre.ca
FIND previous PLUGIN versions
Viewing the plugin trunk and
selecting the Revision Log

31.
@ylefebvre
ylefebvre.ca
FIND previous PLUGIN versions
Select latest version in left column and known
working version in right column

32.
@ylefebvre
ylefebvre.ca
FIND previous PLUGIN versions
Click View changes

33.
@ylefebvre
ylefebvre.ca
FIND previous PLUGIN versions

34.
@ylefebvre
ylefebvre.ca
FIND previous PLUGIN versions
At page bottom, download archive containing
old versions of changed files

35.
@ylefebvre
ylefebvre.ca
FIND previous PLUGIN versions
● Once you have the previous version
– Upload to your server via FTP
– Stop updating until you see a message
indicating that the issue has been resolved

36.
@ylefebvre
ylefebvre.ca
Avoiding bad plugin breakups
● User-triggered breakup
– Better solution available
– Extra functionality no longer required
● Plugin-triggered breakup
– Plugin converted to paid model
– End of development life
– Lack of support for new versions

37.
@ylefebvre
ylefebvre.ca
Avoiding bad plugin breakups
● Many plugins store user information to the
database to provide additional capabilities
– Custom fields
– Custom post types
– Custom tables
● Not all developers consider what will happen
if users decide to stop using their plugin

38.
@ylefebvre
ylefebvre.ca
Avoiding bad plugin breakups
● Before deploying plugins, analyze the
effects of deactivation to prepare for
eventual breakup
– Clean removal
– Ease or difficulty of accessing custom data
– Core data modifications
– Broken site

39.
@ylefebvre
ylefebvre.ca
Conclusions
● Plugins are amazing tools that can greatly
enhance your site
● Plugins are potential liabilities that can break
your site
● When used with caution, plugins bring
limitless possibilities to web site creation

40.
@ylefebvre
ylefebvre.caBryanBerg,Architect

41.
@ylefebvre
ylefebvre.ca
Recommended Readings
● Learn about plugin development
– WordPress Plugin Development
Cookbook by Yannick Lefebvre,
published by Packt Publishing
(packtpub.com)
– Use code WCMONTREAL13 to get 75%
off ebook on packtpub.com (until Aug 1)
● Find help when you run into issues
– WordPress Support Forum
(wordpress.org/support)
● Today's presentation available at:
– http://yannickcorner.nayanna.biz/wcmtl2013

42.
@ylefebvre
ylefebvre.ca
Thank you for attending this talk
on Plugins
Questions?
Presentation: http://yannickcorner.nayanna.biz/wcmtl2013
ylefebvre@gmail.com
profiles.wordpress.org/users/jackdewey
Use code
WCMONTREAL13
to get 75 off%
WordPress Plugin
Development
Cookbook ebook
on packtpub.com
(until Aug 1)