Uncaught Error: Class 'WP_Query' not found in url - Wordpress

Question

i created an ajax file that pass ID in the page. and that page has a query. and i got an error. I try to know what is my error and some site said i have to define my template and require the wp-load.php, but some site said that i have to do it on function.php. and i really don't know what to do. i'm new in wordpress woocommerce.

Uncaught Error: Class 'WP_Query' not found in xxxx/xxxx

Here is my Page (get-fabric.php)

   <?php  


    if(!empty($_POST['select_colour']))
    {
        $args = array(
        'post_type'      => 'product',
        'posts_per_page' => 1000,
        'product_cat'    => 'fabric'


        );

        $query = new WP_Query($args);


            while ( $query->have_posts() ) : $query->the_post();
            global $product;
            $regular_price = $product->get_price_html();

            $image = wp_get_attachment_image_src( get_post_thumbnail_id( $query->post->ID ), 'product' );
                echo '  <div class="col-md-3 fabric-active" data-fabcode="32860">
                <div class="fabric-cloth">
                    <div class="fabric-data">
                        <img src="'.$image[0].'" class="img-responsive cursor-on" />
                        <div class="fabric-code">
                            <p>'.$product->post->post_title.'</p>
                            <span>'.$regular_price.'</span>
                        </div>
                    </div>
                </div>
            </div>';
            endwhile;

    wp_reset_query();
    ?>
    <div class="col-md-3 fabric-active" data-fabcode="32860">
                <div class="fabric-cloth">
                    <div class="fabric-data">
                        <img src="'.$image[0].'" class="img-responsive cursor-on" />
                        <div class="fabric-code">
                            <p>'.$product->post->post_title.'</p>
                            <span>'.$regular_price.'</span>
                        </div>
                    </div>
                </div>
            </div>
  <?php
     }
  ?>

Answer 1

If you are calling this url directly, which is not how WordPress ajax is intended to work, you can still get this code to run by adding this php code

$parse_uri = explode( 'wp-content', $_SERVER['SCRIPT_FILENAME'] );
require_once( $parse_uri[0] . 'wp-load.php' );

to the top of the file.

https://codex.wordpress.org/AJAX_in_Plugins I know this says Ajax in plugins but this is also what you would do if developing a custom theme to keep your code WordPress-y.