I have 2 dropdown lists, when a user select value in the first list, there is an ajax call to a function using WP_query which send results to populate the second dropdown.

My WP_query is not returning any result. I\'m new to WP_query so I should have made a mistake somewhere.

The query should return the posts having the meta_key _wpcf_belongs_marque-type_id with the meta_value equal to the parent id sent by ajax. The posts should also have the post_type \'aromes-type\'.

Here is the function located in my functions.php:

wp_enqueue_script( \'my-ajax-request\', get_template_directory_uri() . \'/js/ajax.js\', array( \'jquery\' ) );
wp_localize_script( \'my-ajax-request\', \'MyAjax\', array( \'ajaxurl\' => admin_url( \'admin-ajax.php\' ) ) );
add_action( \'wp_ajax_brand_children\', \'GetBrandChildren\');
add_action( \'wp_ajax_nopriv_brand_children\', \'GetBrandChildren\');



function GetBrandChildren() {

    $output = \'\';
    //retrieve POST data sent by AJAX
    $parent_id = $_GET[\'parent_id\'];

    //Define query arguments
    $args = array(
    \'post_type\'  => \'aromes-type\',
    \'meta_query\' => array(
        \'relation\' => \'AND\',
                array(
                    \'key\'     => \'_wpcf_belongs_marque-type_id\',
                    \'value\'   => $parent_id
                ),
            ),
    \'posts_per_page\' => -1
    );


    //Create the query
    $the_query = new WP_Query( $args );

    // The Loop
    if ( $the_query->have_posts() ) :
        while ( $the_query->have_posts() ) : $the_query->the_post();
                $output .= \'<option>\' . get_the_title() . \'</option>\';
        endwhile;
    else:
            $output = \'<option>No flavors found...</option>\';
    endif;

    echo $output;

    // Reset Post Data
    wp_reset_postdata();
    wp_die();
}

The JQuery making the call :

//On selected brand, update flavors list
  $(document).on(\'change\', "select[id^=\'marque\']", function() {

        var $brandid =  $(this).val();
        var $brand_dd_id = $(this).attr(\'id\');
        var $flav_dd_id = $brand_dd_id.substr($brand_dd_id.length-1);

        //Make AJAX request, using the selected value as the GET
        $.ajax({
                url: MyAjax.ajaxurl,
                beforeSend: function(){$("#arome"+$flav_dd_id+".ul.select2-results").empty();},
                data: {
                        \'parent_id\': $brandid,
                        \'action\': \'brand_children\'
                      },
                success: function(output) {
                    console.log(output);
                    $("#arome"+$flav_dd_id+".ul.select2-results").append(output);
                    $("#arome"+$flav_dd_id).trigger("chosen:updated");
                },
                error: function (xhr, ajaxOptions, thrownError) {
                    alert(xhr.status + " "+ thrownError);
        }});

});