Ajax - Call to undefined function get_option()

Question

So I've been working in Wordpress lately with Ajax and I managed to get some stock data into my site from my database. However, I am now trying to use Ajax to load Wordpress posts into my left sidebar, which requires the use of Wordpress functions and it seems as if I am not doing this properly.

I have gone through the Wordpress Codex and several other threads/tutorials about this topic, however I am extremely confused about what I am doing wrong.

Javascript File

function load_blog_posts_function() 
{
     jQuery.ajax({
     url: "wp-content/themes/Divi/js/stockchart/blog-list-query.php",
     data: ({action : 'load_blog_posts_sidebar'}),
     success: function(data) {
     alert(data);
     }
     });
}

PHP File

<?php 
function load_blog_posts_sidebar()
{
$stockSymbol = $_GET['symbol'];
/* Set up the query arguments. */
$options = get_option("widget_rpwe_widget");
$args = array('fb' => $cat);
$default_args = apply_filters( 'rpwe_default_query_arguments', $args );
$rpwewidget = get_posts($default_args);
//echo $options;
echo("hello world");
}
?>

I also read that some code was needed in my functions.php, so I have this:

$dirName = dirname(__FILE__);
$baseName = basename(realpath($dirName));
require_once ("$dirName/js/stockchart/blog-list-query.php");

add_action("wp_ajax_nopriv_load_blog_posts_sidebar", "load_blog_posts_sidebar");
add_action("wp_ajax_load_blog_posts_sidebar", "load_blog_posts_sidebar");

I currently get two errors when I try to run this, the more important one is

Call to undefined function get_option()

which tells me that my php script is not recognizing Wordpress functions and I also get this one:

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at .../www.3weekwebsites.com/wp-content/themes/Divi/js/stockchart/blog-list-query.php:12) in .../www.3weekwebsites.com/wp-content/themes/Divi/header.php on line 1

Could anyone please share some insight here? I would really appreciate it. :)

Answer 1

You're firing a request to a PHP file that won't have the WordPress library loaded - hence the undefined function error.

You could manually load in WordPress with something like require '../../../wp-load.php'.

Or, better yet, use the awesome AJAX API. Just fire your request to wp-admin/admin-ajax.php and then register a callback in your plugin or theme that matches the action parameter (in your case, load_blog_posts_sidebar):

function wpse_147692_load_blog_posts_sidebar() {
    // Do something!
    exit;
}

add_action( 'wp_ajax_nopriv_load_blog_posts_sidebar', 'wpse_147692_load_blog_posts_sidebar' );
add_action( 'wp_ajax_load_blog_posts_sidebar',        'wpse_147692_load_blog_posts_sidebar' );