Here’s a very lengthy answer of my own question that goes beyond just addressing the question of generating unique nonces for subsequent Ajax requests. This is an “add to favorites” feature that was made generic for the purposes of the answer (my feature lets users add the post IDs of photo attachments to a list of favorites, but this could apply to a variety of other features that rely on Ajax). I coded this as a standalone plugin, and there are a few items missing– but this should be enough detail to provide the gist if you want to replicate the feature. It will work on an individual post/page, but it’ll also work in lists of posts (e.g. you can add/remove items to favorites inline via Ajax and each post will have its own unique nonce for each Ajax request). Keep in mind that there’s probably a more efficient and/or more elegant way to do this, and currently this works for Ajax only– I haven’t bothered yet to process non-Ajax $_POST data.
scripts.php
/**
* Enqueue front-end jQuery
*/
function enqueueFavoritesJS()
{
// Only show Favorites Ajax JS if user is logged in
if (is_user_logged_in()) {
wp_enqueue_script('favorites-js', MYPLUGIN_BASE_URL . 'js/favorites.js', array('jquery'));
wp_localize_script('favorites-js', 'ajaxVars', array('ajaxurl' => admin_url('admin-ajax.php')));
}
}
add_action('wp_enqueue_scripts', 'enqueueFavoritesJS');
favorites.js (Lots of debug stuff that can be removed)
$(document).ready(function()
{
// Toggle item in Favorites
$(".faves-link").click(function(e) {
// Prevent self eval of requests and use Ajax instead
e.preventDefault();
var $this = $(this);
console.log("Starting click event...");
// Fetch initial variables from the page
post_id = $this.attr("data-post-id");
user_id = $this.attr("data-user-id");
the_toggle = $this.attr("data-toggle");
ajax_nonce = $this.attr("data-nonce");
console.log("data-post-id: " + post_id);
console.log("data-user-id: " + user_id);
console.log("data-toggle: " + the_toggle);
console.log("data-nonce: " + ajax_nonce);
console.log("Starting Ajax...");
$.ajax({
type: "POST",
dataType: "json",
url: ajaxVars.ajaxurl,
data: {
// Send JSON back to PHP for eval
action : "myFavorites",
post_id: post_id,
user_id: user_id,
_ajax_nonce: ajax_nonce,
the_toggle: the_toggle
},
beforeSend: function() {
if (the_toggle == "y") {
$this.text("Removing from Favorites...");
console.log("Removing...");
} else {
$this.text("Adding to Favorites...");
console.log("Adding...");
}
},
success: function(response) {
// Process JSON sent from PHP
if(response.type == "success") {
console.log("Success!");
console.log("New nonce: " + response.newNonce);
console.log("New toggle: " + response.theToggle);
console.log("Message from PHP: " + response.message);
$this.text(response.message);
$this.attr("data-toggle", response.theToggle);
// Set new nonce
_ajax_nonce = response.newNonce;
console.log("_ajax_nonce is now: " + _ajax_nonce);
} else {
console.log("Failed!");
console.log("New nonce: " + response.newNonce);
console.log("Message from PHP: " + response.message);
$this.parent().html("<p>" + response.message + "</p>");
_ajax_nonce = response.newNonce;
console.log("_ajax_nonce is now: " + _ajax_nonce);
}
},
error: function(e, x, settings, exception) {
// Generic debugging
var errorMessage;
var statusErrorMap = {
'400' : "Server understood request but request content was invalid.",
'401' : "Unauthorized access.",
'403' : "Forbidden resource can't be accessed.",
'500' : "Internal Server Error",
'503' : "Service Unavailable"
};
if (x.status) {
errorMessage = statusErrorMap[x.status];
if (!errorMessage) {
errorMessage = "Unknown Error.";
} else if (exception == 'parsererror') {
errorMessage = "Error. Parsing JSON request failed.";
} else if (exception == 'timeout') {
errorMessage = "Request timed out.";
} else if (exception == 'abort') {
errorMessage = "Request was aborted by server.";
} else {
errorMessage = "Unknown Error.";
}
$this.parent().html(errorMessage);
console.log("Error message is: " + errorMessage);
} else {
console.log("ERROR!!");
console.log(e);
}
}
}); // Close $.ajax
}); // End click event
});
Functions (front-end display & Ajax action)
To output the Add/Remove Favorites link, simply call it on your page/post via:
if (function_exists('myFavoritesLink') {
myFavoritesLink($user_ID, $post->ID);
}
Front-end display function:
function myFavoritesLink($user_ID, $postID)
{
global $user_ID;
if (is_user_logged_in()) {
// Set initial element toggle value & link text - udpated by callback
$myUserMeta = get_user_meta($user_ID, 'myMetadata', true);
if (is_array($myUserMeta['metadata']) && in_array($postID, $myUserMeta['metadata'])) {
$toggle = "y";
$linkText = "Remove from Favorites";
} else {
$toggle = "n";
$linkText = "Add to Favorites";
}
// Create Ajax-only nonce for initial request only
// New nonce returned in callback
$ajaxNonce = wp_create_nonce('myplugin_myaction_' . $postID);
echo '<p class="faves-action"><a class="faves-link"'
. ' data-post-id="' . $postID
. '" data-user-id="' . $user_ID
. '" data-toggle="' . $toggle
. '" data-nonce="' . $ajaxNonce
. '" href="#">' . $linkText . '</a></p>' . "\n";
} else {
// User not logged in
echo '<p>Sign in to use the Favorites feature.</p>' . "\n";
}
}
Ajax action function:
/**
* Toggle add/remove for Favorites
*/
function toggleFavorites()
{
if (is_user_logged_in()) {
// Verify nonce
$ajaxNonce="myplugin_myaction" . $_POST['post_id'];
if (! wp_verify_nonce($_POST['_ajax_nonce'], $ajaxNonce)) {
exit('Sorry!');
}
// Process POST vars
if (isset($_POST['post_id']) && is_numeric($_POST['post_id'])) {
$postID = $_POST['post_id'];
} else {
return;
}
if (isset($_POST['user_id']) && is_numeric($_POST['user_id'])) {
$userID = $_POST['user_id'];
} else {
return;
}
if (isset($_POST['the_toggle']) && ($_POST['the_toggle'] === "y" || $_POST['the_toggle'] === "n")) {
$toggle = $_POST['the_toggle'];
} else {
return;
}
$myUserMeta = get_user_meta($userID, 'myMetadata', true);
// Init myUserMeta array if it doesn't exist
if ($myUserMeta['myMetadata'] === '' || ! is_array($myUserMeta['myMetadata'])) {
$myUserMeta['myMetadata'] = array();
}
// Toggle the item in the Favorites list
if ($toggle === "y" && in_array($postID, $myUserMeta['myMetadata'])) {
// Remove item from Favorites list
$myUserMeta['myMetadata'] = array_flip($myUserMeta['myMetadata']);
unset($myUserMeta['myMetadata'][$postID]);
$myUserMeta['myMetadata'] = array_flip($myUserMeta['myMetadata']);
$myUserMeta['myMetadata'] = array_values($myUserMeta['myMetadata']);
$newToggle = "n";
$message = "Add to Favorites";
} else {
// Add item to Favorites list
$myUserMeta['myMetadata'][] = $postID;
$newToggle = "y";
$message = "Remove from Favorites";
}
// Prep for the response
// Nonce for next request - unique with microtime string appended
$newNonce = wp_create_nonce('myplugin_myaction_' . $postID . '_'
. str_replace('.', '', gettimeofday(true)));
$updateUserMeta = update_user_meta($userID, 'myMetadata', $myUserMeta);
// Response to jQuery
if($updateUserMeta === false) {
$response['type'] = "error";
$response['theToggle'] = $toggle;
$response['message'] = "Your Favorites could not be updated.";
$response['newNonce'] = $newNonce;
} else {
$response['type'] = "success";
$response['theToggle'] = $newToggle;
$response['message'] = $message;
$response['newNonce'] = $newNonce;
}
// Process with Ajax, otherwise process with self
if (! empty($_SERVER['HTTP_X_REQUESTED_WITH']) &&
strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest') {
$response = json_encode($response);
echo $response;
} else {
header("Location: " . $_SERVER["HTTP_REFERER"]);
}
exit();
} // End is_user_logged_in()
}
add_action('wp_ajax_myFavorites', 'toggleFavorites');