Wordpress and wp_ajax

PHP
1

I want to use $WPDB class outside Wordpress context in an external Ajax handling script.

For this in general is needed to load the core Worpdress files.

After loading those core files I can make calls to the MySQL tables using the $wpdb class, but loading the core Wordpress files is a lot of overhead just to run a couple of queries. I was looking for a better solution and I find ‘wp_ajax’
and ‘wp_ajax_nopriv’ hooks, but on Wordpress site and on Google I couldn’t find any good documentation or tutorial.

I need to transfer, using ajax, back and forth data as Json.
Could anyone provide me with more information or a good example about this?
Thx

2

This quick URL I found covers it, there’s not much to do:

  1. Add a function to a plugin that you want to be available through AJAX
  2. Register it with add_action(“wp_ajax_make_up_this_part”, “your_function_name”);
  3. Call that function from JavaScript by POSTing to /wp-admin/admin-ajax.php with “action” parameter equal to the name you defined in step 2
3

Thx, but I know that tutorial.I searched 3 days on google.My situation is a little different, plus the tutorial is not complete, the author wrote “continue… next post I will show you the full plugin code” , but doesn’t exist a next post.For the moment I’m not creating a plugin.

But maybe, you can help me, if i didn’t understand correctly the tutorial.

In wordpress functions.php file I have a function which control a form, which can have tens to hundreds of fields.This function is used to modify different fields in all the site(pages and posts). It is a mass editing function.On submit on the form, with jquery $post I send Json data to a script, that send me back json data, as array.

This script need to use $wpdb.In his case the author use only 1 file, by redirecting the ajax call thru wordpress admin-ajax.php.In my case are 2 files implied, and for the moment I didn’t have an working solution

4

You don’t need anything else but what’s in that tutorial.

Your “mass editing function” is the function you register with add_action (step 2). Then your AJAX call posts the form to admin-ajax.php with an “action” equal to the name you used when registering your “mass editing function” (step 3).

That’s everything…

5

It is not working; The values are send correct but for the response I get (Firebug) zero.The code is working loading wordpress core.

Front-end in functions.php

<script>
    $j=jQuery.noConflict();
    $j('document').ready(function(){
    $j('#custom_select_seo').change(function(){
        $j.post('admin-ajax.php', {action:"select", option: $j('#custom_select_seo').val(),custom_select: "custom_select"},
            function(data){
              for (var i in data) {
           $j("#edit_"+data[i][0]).val(data[i][1]);
                i++;
           $
                  }
            }, 'json');
    })
});
</script>
        <?php add_action("wp_ajax_select", "my_ajax_update"); ?>

The php script is located at the same level in theme file:

<?php

function my_ajax_update() {
if ($_POST['custom_select']=='custom_select')
$ld=loadInfo ($_POST['option']);
}

    function loadInfo ($option){
    global $wpdb;
    switch ($option) {
    case 'title':

          $res=$wpdb->get_results("SELECT  {$wpdb->posts}.ID AS ID,{$wpdb->posts}.post_title ,
                                {$wpdb->postmeta}.meta_value AS meta_value
                                FROM {$wpdb->posts}
                                JOIN {$wpdb->postmeta} ON {$wpdb->posts}.ID={$wpdb->postmeta}.post_id
                                AND {$wpdb->posts}.post_type='post'AND  {$wpdb->postmeta}.meta_key='title'");

    break;
    case 'description':

          $res=$wpdb->get_results("SELECT  {$wpdb->posts}.ID AS ID,{$wpdb->posts}.post_title ,
                                {$wpdb->postmeta}.meta_value AS meta_value
                                FROM {$wpdb->posts}
                                JOIN {$wpdb->postmeta} ON {$wpdb->posts}.ID={$wpdb->postmeta}.post_id
                                AND {$wpdb->posts}.post_type='post'AND  {$wpdb->postmeta}.meta_key='description'");
    break;
    case 'keywords':

          $res=$wpdb->get_results("SELECT  {$wpdb->posts}.ID AS ID,{$wpdb->posts}.post_title ,
                                {$wpdb->postmeta}.meta_value AS meta_value
                                FROM {$wpdb->posts}
                                JOIN {$wpdb->postmeta} ON {$wpdb->posts}.ID={$wpdb->postmeta}.post_id
                                AND {$wpdb->posts}.post_type='post'AND  {$wpdb->postmeta}.meta_key='keywords'");
    break;

    }
    $i=1;
    foreach ($res as $seo) {
     $list[$i]=array($seo->ID,$seo->meta_value);
     $i++;
    // $list['edit_'.$seo->ID][ID]=$seo->ID;
     //$list['edit_'.$seo->ID][$_POST['option']]=$seo->meta_value;
    }
    $str=json_encode($list);
echo $str;

}

?>
6

After some tests I observed that the solution is working if everything is on the same file.