WordPress Actions vs. Filters

September 6, 2012

If you’re still wondering about the difference between WordPress actions and WordPress filters, Michael Fields posted a very cool explanation in this forum thread called Actions vs. Filters. I think it’s the best explanation of actions and filters I have seen so far, well done Michael, and keep up the good work!

Let’s pretend that WordPress is a Mexican restaurant and we have ordered a taco as illustrated by the following code…
<?php $taco = 'chicken'; ?>

Hat tip to Philip for finding this little two-year old treasure in the forums. If you’re interested in a very detailed article about the internals of actions and filters, check out Gennady’s post called Inside WordPress Actions and Filters.

Has anyone else stumbled across interesting ways of describing WordPress functions and APIs? Feel free to share your links!

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About the author

Konstantin Kovshenin

WordPress Core Contributor, ex-Automattician, public speaker and consultant, enjoying life in Moscow. I blog about tech, WordPress and DevOps.

8 comments

Slobodan Manic (@slobodanmanic) says:

September 6, 2012 at 11:13 am

Probably not as good, and definitely oversimplified (and written by me):

Once again, that last block of code in plain English – “Hey WordPress, when you run register_form hook, would you be so kind to show these fields as well? Thanks!“. Kinda like, “Honey, since you’re going out to a bar, could you take out the trash as well?” but more techy. It’s adding a function (taking out the trash) to your action (going out). The filter function is different, what it says is “Honey, now that you’re going to take out the trash, could you take this heavy old chair that we don’t need as well?” – you’re still taking out the trash, it’s just a little bit different – your output (pun, pun) is being filtered!

http://thematosoup.com/development/additional-contact-fields-wordpress-registration-form/

(hope you don’t mind the URL, but it’s out of context posted like this)
- Konstantin Kovshenin says:
  
  September 6, 2012 at 11:24 am
  
  Oh hey Slobodan, that’s awesome! Thanks for sharing the link and great analogy with taking the trash out, I love it :)
Slobodan Manic (@slobodanmanic) says:

September 6, 2012 at 11:27 am

And thanks for editing the comment to add the quote :)
Jeremy says:

September 6, 2012 at 1:46 pm

I remember that I learned a lot from a post on Nathan Rice’s blog, a few years ago:
http://www.nathanrice.net/blog/an-introduction-to-wordpress-action-hooks/

But Michael’s explanation is pretty good!
- Konstantin Kovshenin says:
  
  September 6, 2012 at 1:58 pm
  
  Thanks for sharing that Jeremy, it does look like a decent explanation of actions and filters. However, the CSS code snippets that use the heredoc syntax will break because of indentation:
  
  It is very important to note that the line with the closing identifier must contain no other characters, except possibly a semicolon. That means especially that the identifier may not be indented
  
  Not really related to the topic, but just as a heads up ;)
  
  Thanks for your comment!
Kirk Wight says:

September 12, 2012 at 5:29 pm

I recently drew pictures, which people seemed to grasp (who doesn’t like stick men?): http://wordpress.tv/2012/09/09/kirk-wight-getting-started-with-theme-development/
- Konstantin Kovshenin says:
  
  September 13, 2012 at 6:39 am
  
  Oh wow, that looks great Kirk, brilliant explanation through visuals :) Thanks for sharing!
- Kirk Wight says:
  
  September 13, 2012 at 7:24 am
  
  I think the action example could still be better; they should be less related (eg. paint a landscape, order pizza). Next time…