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I've written a simple plugin that works on a clean install. All it does is once a page is loaded it requests some ajax via admin-ajax.php and then outputs the returned data to the console. When I put on the site I am working which is nothing out of the ordinary it just some custom post types it only works if I am logged in.

When the function that generates the ajax output test_ajax_process_request() is called via wp_ajax_test_ajax when user is logged in it works fine, the console shows what is loaded from admin-ajax.php. But if I am not logged in wp_ajax_nopriv_test_ajax seems to not call test_ajax_process_request(), I know this as I am using error_log to trace when test_ajax_process_request() called. Usually if there is a problem admin-ajax.php will just return a 0 but in this case it's returning my thame's HTML.

My plugin is made of 2 files: ajax_test.php:

<?php
/*
Plugin Name:  Simple AJAX test 2018-05-22
Author:       Kevin Meredith
Description:  Pluggin to test client site AJAX request
Version:      1
*/

// disable direct file access
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

function load_js() {

    wp_enqueue_script('ajax_test', plugin_dir_url( __FILE__ ) . 'ajax_test.js', array('jquery'), null, true );

     $test_nonce = wp_create_nonce('test_nonce');
    wp_localize_script(
        'ajax_test',
        'wbs_ajax_obj',
        array(
            'ajax_url' => admin_url( 'admin-ajax.php' ),
            'nonce'    => $test_nonce,
        )
    );
    error_log('Load JS TEST SITE');
    // wp_localize_script is used to send an array of php values to javascript
    // it embeds values in the HTML so that be used by java script
}
add_action( 'wp_enqueue_scripts', 'load_js' );  

function test_ajax_process_request() {
    error_log('test_ajax_process_request() has been called');
    // first check if data is being sent and that it is the data we want
    //check_ajax_referer( $action, $query_arg, $die )
    if ( check_ajax_referer( 'test_nonce', 'js_nonce', false) ) {
        // 1st parameter is the were the nonce is stored in the $_POST array or what the nonce from field name
        // 2nd parameter is the name of the nonce which is set up in wp_create_nonce()
        // 3rd parameter is die, if true and nonce fails they function will return false
        $ran = rand(0, 100);
      $return_string = 'string from JS: "'.$_POST["from_js"].'" random number from server: '.$ran.' nonce: '.$_POST["js_nonce"].' TEST SITE';
      error_log($return_string);
      echo $return_string;
        die();
    }else{
      $return_string = 'nonce fail (ajax_test.php)';
        echo ($return_string);
      error_log($return_string);
        die();
    }
}
add_action('wp_ajax_test_ajax', 'test_ajax_process_request');
add_action('wp_ajax_nopriv_test_ajax', 'test_ajax_process_request');

And my JS file: ajax_test.php

var $ = jQuery.noConflict();

$( document ).ready(function() {

    console.log('Nonce: '+wbs_ajax_obj.nonce+' from ajax_test.js');

    $.ajax({
      type:"POST",
      url: wbs_ajax_obj.ajax_url, // 'https://lomokev.com/ajaxtest'
      data: {
          action: "test_ajax", // name of the wordpress hook that will trigger function so in this case wp_ajax_nopriv_test_ajax and wp_ajax_test_ajax'
          js_nonce: wbs_ajax_obj.nonce,
          from_js: 'value of from_js from ajax_test.js'
      },
      success:function(data){
        console.log(data);
      },
      error: function(errorThrown){
          console.log(Object.values(errorThrown));
      } 

    });

    // if it's a 404 the error says "error"
    // but this says "Bad Request"

});

out from logged in and none logged in user

  • Have you considered using a REST API endpoint instead? They're much easier to debug, and much more secure – Tom J Nowell May 22 '18 at 14:13
  • I’ve also come to that conclusion myself it's just a little annoying because spent time learning how to do it this way ;-). – lomokev May 22 '18 at 15:02
  • Is there a chance that some other plugin already registered action wp_ajax_nopriv_test_ajax? It's a pretty common name, so there is such chance, I guess. In such case the response can be generated not by your function. You can change priority of your hook. – Krzysiek Dróżdż May 23 '18 at 5:45
  • 1
    @KrzysiekDróżdż I did it on a clean install so the hook was not clashing, that said it's a really good point test_ajax is an obvious name for ajax hook ;-) I did figure it out I had some code that was redirecting none logged in users away from the wp-admin which would include admin-ajax.php see my answer below if your interested. – lomokev May 23 '18 at 20:53
3

Found the solution, reason why it was returning HTML is because it was doing a 302 redirect to the home page.

Turns out that I had a function in my theme that redirects none logged in users away from the wp-admin pages which is where admin-ajax.php is.

<?php
    // IF SUSBSCIBER GOES TO ADMIN /wp-admin THEY ARE REDIRCTED TO THE HOME PAGE START : this code works as of 2018-01-29 (no plugins)

      /**
      * Redirect back to homepage and not allow access to
      * WP admin for Subscribers.
      */

     function themeblvd_redirect_admin(){
          if ( ! current_user_can('delete_published_posts')) { // changed from edit_posts so that it works for contibuters to
               wp_redirect( site_url() );
               exit;         
          }
     }
     add_action( 'admin_init', 'themeblvd_redirect_admin' );
?>

I have it there for testing, so if have testing with a holding page I allow clients to login using a subscriber account, once they are logged in they are redirected to the home page instead of seeing the there user page. I found the solution for this once I released it was a 302 redirect, I found this thread on the subject: https://stackoverflow.com/questions/9408334/wordpress-admin-ajax-results-in-error-302-redirect

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