Developers have spent countless hours working on a plugin that seems to be built just for you, just for this moment. If only it wouldn’t…. This is a problem nearly every developer faces at some point during a project. Knowing how to safely customize functionality is key to building products that will stand the test of time (or major updates.) This talk will cover the following topics: Hooks Filters Overwriting Functions Modifying Returned content Requesting a change to a plugin This talk will define and provide a use case for each of the possible pathways listed above. This presentation is for beginning to intermediate developers and though I will use as little code as possible, given the nature of this talk I would imagine each item will require 1 code example. The slides will be available ahead of time on slideshare and the code examples will be available on GitHub.

1. Playing Ball With
Plugins
Navigating and Extending Large Codebases:
A Field Guide
https://marcgratch.com | mgratch
WordCamp Boston 2017

2. Defining Your Problem
Make sure you’re solving a real problem
https://marcgratch.com | mgratch
WordCamp Boston 2017

3. Make sure you’re solving a real problem
• Is this behavior self-inflicted or inherent to the
plugin?
• Does this (will this) behavior bother the client? (Or is
it just me?)
• Will this impact launch?
• Can it be fixed with a bit of CSS?
https://marcgratch.com | mgratch
WordCamp Boston 2017

4. Be Aware: Dangerous Territory
Extending another plugin can get messy
https://marcgratch.com | mgratch
WordCamp Boston 2017

5. Some “dangers” of Extending/Integrating with
a 3rd Party Plugin
•Is the plugin regularly maintained?
•Are the plugin updates (typically) backwards
compatible?
•Did you ensure your code is maintainable?
https://marcgratch.com | mgratch
WordCamp Boston 2017

6. READ THE DOCS!
Seriously…
https://marcgratch.com | mgratch
WordCamp Boston 2017

7. Find a Good Place to Start:
Defining your Goal
• Making a Change on the Frontend:
• Determine what file manages where (or near) your final code will need to output (or
need to modify.)
• Look at the source code (in the browser)
• Find unique strings to search for. (HTML classes or IDs are usually a good place to
start.)
• Search the plugins code base for this unique string.
https://marcgratch.com | mgratch
WordCamp Boston 2017

8. Find a Good Place to Start:
Defining your Goal
• Making a Change on the Backend:
• READ THE DOCS
• Try to identify the function(s)handling the data you wish to change.
• Search All Files in the Plugin for `apply_filters` or `do_action`
• USE BREAK POINTS / XDEBUG / STEP THROUGH
https://marcgratch.com | mgratch
WordCamp Boston 2017

9. Hooks: They’re Magical
Nothing clever here… they really are.
https://marcgratch.com | mgratch
WordCamp Boston 2017

10. Hooks: They’re Magical
• Event Driven Programming
• Complex Changes Without Modifying Core Files
• Modify Data at the Source
• Upgrade Safely (typically)
• Backwards Compatible!!!! (typically)
https://marcgratch.com | mgratch
WordCamp Boston 2017

11. Pluggable Functions &
Overriding templates
The dangers within.
https://marcgratch.com | mgratch
WordCamp Boston 2017

12. Overriding Functions: Pluggable Functions
if ( ! function_exists( ‘some_function’ ) ) {
// do something different
}
• You can only do this once
• Only works as long as the pluggable function exists
https://marcgratch.com | mgratch
WordCamp Boston 2017

13. Pluggable “Template” Files
• When the original file is updated… yours will
remain. Old & Outdated.
• Multiple implementations are problematic.
• Only works as long as the original file exists/used
or no longer performs its intended function.
https://marcgratch.com | mgratch
WordCamp Boston 2017

14. Modifying Returned Content
• DO NOT MODIFY HTML WITH str_replace()
• Browsers are lenient – not all HTML is written the same.
• Modifying return HTML requires
DOMDocument Class
• Make sure the `class_exists(‘DOMDocument’)`
https://marcgratch.com | mgratch
WordCamp Boston 2017

15. If All Else Fails: Write a Patch
Then ask the plugin developers to implement it…
https://marcgratch.com | mgratch
WordCamp Boston 2017

16. Asking for a Change to the Core Plugin:
•Be Polite
•Identify if it’s an Edge Case
•Explain the Reason for your Patch
•Offer to fix another bug if you can…
https://marcgratch.com | mgratch
WordCamp Boston 2017

17. Asking for a Change to the Core Plugin:
…the other reason I was reaching out was in regards to submitting patches. I
realize it is likely an edge case, but I am hopeful that you might be willing to
consider implementing the attached patch. It simply adds the ability to add custom
fields (or content) to the bottom of the `getImageTab` output. I have tested it and
written further unit tests for it. The patch appears to work as expected.
Furthermore, I am familiar with your code base and I am happy to help with any
other bugs or roadmap features as I continue to work with your plugin…
https://marcgratch.com | mgratch
WordCamp Boston 2017

18. Asking for a Change to the Core Plugin:
First let me say I have been using your plugin since 2012 and I am always happy
to support good plugins and their authors.
I am hopeful you are willing to consider implementing the attached patch. It
allows form submission via AJAX. I am building a single page app and
honestly your plugin does everything I need except post back is killing the
experience. I have tested it on a vanilla WP install and it seems to be working.
If you run unit tests I am happy to write a few for this new functionality as
well…
https://marcgratch.com | mgratch
WordCamp Boston 2017

19. Great Resources
wptavern.com make.wordpress.org tommcfarlin.com
poststatus.com wordpress.tv pippinsplugins.com
joshpress.net wpchat.com carriedils.com
tuts+ wpbeginner.com carlalexander.ca
torquemag.io wpmayor.com yoast.com
wpshout.com helenhousandi.com gravitywiz.com
wplift.com chrislema.com webdevstudios.com
hookr.io
https://marcgratch.com | mgratch
WordCamp Boston 2017