After doing some extensive research, I've exhausted all my options and decided to actually ask a question here. I'm trying to get a filtered set of posts through AJAX using WP_Query and the tax_query parameter.

I currently have one custom post type called "Vocabulary Terms" and two custom taxonomies called "vocabulary categories" and "difficulty level". Essentially what I want users to do is select a category, then a difficulty level and load any of the posts that are tagged with each. Below are my php functions and js. It seems I can filter by Vocabulary Terms but the second I attempt to pass anything into tax_query, it fails.

Any ideas?


function get_game_difficulty() {

// Nonce check
$nonce = $_REQUEST['nonce'];
if (!wp_verify_nonce($nonce, 'ajax_scripts_nonce')) die(__('Busted.'));

global $wpdb;
global $wp_query;
global $post;
global $terms;

$html = "";
$success = false;
$gameCategory = $_REQUEST['gameCategory'];
$gameDifficulty = $_REQUEST['gameDifficulty'];

$html .= '<h2>Listen and repeat each word you hear until you feel comfortable pronouncing each word.</h2>';
$html .= $gameCategory;
$html .= $gameDifficulty;

$html .= '<ul>';
$args = array(
    'numberposts' => 5,
    'post_type' => 'vocabulary_terms',
    'tax_query' => array(
            'taxonomy' => 'vocabulary_categories',
            'field' => 'slug',
            'terms' => $gameCategory
$myposts = get_posts( $args );
foreach( $myposts as $post ) :  setup_postdata($post);
    $title = get_the_title();
    $html .= '<li>'.$title.'</li>';
$html .= '</ul>';

// Build the response...
$success = true;
$response = json_encode(array(
    'success' => $success,
    'html' => $html

// Construct and send the response
header("content-type: application/json");
echo $response;
add_action('wp_ajax_nopriv_get_game_difficulty', 'get_game_difficulty' );
add_action('wp_ajax_get_game_difficulty', 'get_game_difficulty' );


$(document).on('click', '#vocabulary-games a.difficulty-level', function() {
//$('#vocabulary-games a.difficulty-level').click(function(){
// Store category slug in variable

var vocab_difficulty = $(this).attr('data-difficulty');
var vocab_cat = $(this).attr('data-category');

// post data to function
$.post(ajax_scripts.ajaxurl, {
    dataType: "jsonp",
    action: 'get_game_difficulty',
    nonce: ajax_scripts.nonce,
    gameDifficulty: vocab_difficulty,
    gameCategory: vocab_cat
  }, function(response) {
    if (response.success===true) {
    } else {
      // Bad Response message
  }); // end click
  • Edit: When I say "it fails", I mean that I don't get any error or any data back from the query. It returns everything up to the point where I get the list.
    – jkhedani
    Dec 9, 2012 at 4:14
  • Are you getting the right slug in $_REQUEST['gameCategory']? Dec 9, 2012 at 6:12
  • Try hard coding a slug for testing. Dec 9, 2012 at 6:13
  • @Rutwick Thanks for the quick reply! (regards for my answer being not as prompt. In testing, I did just hardcode it in and the results were the same. (Side notes: I made sure that the query worked in my template to make sure I wasn't querying empty data and also echoed the POST variable I was passing to make sure it was returning the correct string.) If you have any other ideas, it would be appreciated!
    – jkhedani
    Dec 10, 2012 at 8:12
  • Sorry man. I'm really out of practice with WordPress these days. Couldn't help! Glad you found an answer though! Dec 13, 2012 at 17:22

1 Answer 1


Your code looks fine, but it's failing because your custom taxonomy is not getting registered anywhere in the action hooks of an AJAX call.

My guess is that you are registering your custom taxonomies per the Taxonomies documentation, which tells you to add it to the "init" action hook. However, "init" doesn't get called during an AJAX call. It only gets called during a typical page request or an admin page request (see the Action Reference documentation). (Note: action reference documentation in the codex seems really out of date, it doesn't include any list of actions run during an AJAX request.)

Workaround: where you need access to your custom taxonomies, manually run the init action at the beginning of your ajax function like so:

function get_game_difficulty() {

  // Code that relies on custom taxonomies being registered can be used below.
add_action('wp_ajax_nopriv_get_game_difficulty', 'get_game_difficulty' );
add_action('wp_ajax_get_game_difficulty', 'get_game_difficulty' );
  • This worked wonderfully! You're the best!
    – jkhedani
    Dec 11, 2012 at 0:41

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