Make your WordPress plugin talk AJAX

This morning at BarCamp Cork I gave a short talk on how to add AJAX functionality to WordPress plugins.

Here are the example scripts I used during the talk. Rename the files to .php and install as you would normal WordPress plugins.

  1. helloworld1.txt – very simple and basic “Hello World” plugin.
  2. helloworld2.txt – script that will display the text “Hello World” using an AJAX request to get the text from the server.
  3. helloworld3.txt – script that displays “Hello World” text, and an “update” link that increments a counter via an AJAX http request.
  4. helloworld4.txt – script that displays a simple form. The form has one text box, a “Random” button and a “Save” button. Clicking the “Random” button makes a request to the server to get a random number. “Save” sends the number to the server.
  5. helloworld5.txt and rate.txt – “Rating” script to rate a post (Originally from here). Makes an AJAX request to the server with the rating. Server returns randomly generated stats on rating. Place rate.php in wp-content/

All scripts that operate in the Settings page in the Dashboard use a nonce for security and access admin-ajax.php when making AJAX requests. The wp_ajax_$POST[ ‘action’ ] hook is used to execute the actual code that does something useful.

The rating script uses wp_enqueue_script() to load the jQuery class.

If you’re an Irish O2 user, and use Twitter you might like to install the new Tweet Tweet WordPress plugin. Thanks to Enda who let me use his O2 account briefly, I created a plugin that sends Twitter sms notifications using the free web texts. That means Meteor, Vodafone and O2 are now covered. Anyone want to contribute a plugin for 3?

PS. I was very proud that Automattic was able to sponsor BarCamp Cork, and hopefully most of the WordPress badges found good homes! Conor says 116 signed up for the event, with just over 100 showing up. That’s a great number to pull in for a Saturday tech event!



More photos can be found on and flickr. Looks like Phil hasn’t uploaded any of his shots yet! Can’t wait to see what came of his afternoon photo session. I had to leave early and missed it unfortunately.
Discovered photos of my presentation. Yes, I used Vi (or Vim if you want to be pedantic) to give my talk!

43 thoughts on “Make your WordPress plugin talk AJAX

  1. Thanks 🙂

    I’ve been needing to learn a bit of AJAX for a while now so hopefully these will help break me out of the noob bracket.

  2. Glad they’re a help. My Tweet Tweet plugin uses jQuery too and I found it was hard finding info on how to make AJAX requests while in the dashboard. The nonce stuff required a bit of digging into WordPress code too, but it’s fairly straight forward once you’ve done it once.

  3. Chris – O2 support is the main thing, but the AJAX transition effects when the plugin updates are changed a bit and a settings link is added too.

  4. thecancerus – excellent tutorial. Maybe update it with a section on using a nonce? The security implications of using AJAX without a nonce are severe. A hacker can craft a url and if they trick you into clicking on it they can do bad things to your blog!

  5. Thanks for the tutorial. This is the first one that has made sense to me.

    I have a question regarding the calling of functions within functions…

    For the sake of this example, I am trying to call one of my custom functions from inside the get_randomcol() function. But when I do so, I get the error that my custom function has not been defined. I know it’s defined as I reference it elsewhere and even on the same page as your script runs.

    So is it possible to call non-WP functions from within get_randomcol() and how?


  6. Eric – sure it’s possible, but the file containing the function has to be included first, obviously. Check our code again and don’t give up!

  7. Thanks. I got it figured out. My functions file wasn’t being included because of the way I had included it in my plugin. I’ve fixed that and now it works great.

  8. Does anyone know of any examples for 2.7 for a plugin that works like the Quick Edit or Reply options in the edit comment section of the admin panel? I’m looking to add my own option to that screen that allows an inline form to pop up similar to those.


  9. Hi Donncha,

    I just tested your samples and works great! I was wondering if you can give an example where it gets data from the database? Is that possible?

    Will really appreciate if you can help me on this.

  10. thank you for sharing all these cool examples. when developing a plugin w/ ajax, do you have any sort of backup for people who have javascript disabled? cheers!

  11. Awesome! Thank you so much. This helped me learn how to use AJAX in our Classifeds project to create “chained fields” allowing you to choose a parent category, then AJAX created a new dropdown to allow “child categories” to then be chosen. Many Many thanks.

  12. hi – seems like your .txt files are gone; is that for good? i would love to read what you wrote as it seems by reading the comments quite some clear explanations on wp + ajax
    thanks for your help

  13. Dear Donncha,

    Thank you so much for posting these examples!!!

    My head is done in trying to figure out how to ‘ajaxify’ a calendar plugin for wordpress I’ve (kinda) developed (it’s a lovely looking bit of frankenstein code that has been hobbled together from a number of sources)
    I’ve gotten as far as rendering the calendar with an ajax link but I’m stuck on letting the user navigate between months. This was previously done by passing the month and year in the url with:
    $html .= ‘Next Month > ‘;

    but now that I’m relying on wp and admin-ajax.php, I’m not sure how to specify the url to pass the new month and year variables to. I’m not sure if there is a cache I need to clear from the previous ajax call, or even how to pass a variable to the $(‘.ajax-link’).click(function(){}) that is handling the passing of my variables to the script. (I can get one parameter with a hardcoded value to work but that’s it. example: data { mon: parseInt(‘2’)…}
    I would be SO grateful for some guidance here. There’s fierce little in the way of online resources to find help in. Can I attach the code here?

    1. Chris – unfortunately I probably can’t help you as I’ve forgotten a lot of what I wrote above but I do want to become more familiar with jQuery again as it’s so useful. You should copy your code to a pastebin and post the URL here. You never know, someone who has previously replied here may be able to help.

  14. thanks a million . . . i have been searching for ajax integration in plugins for hours and you provided all the solutions in a single post

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