Retrieve Custom Taxonomies according to posts selected

Question

I have 3 custom taxonomies. The first 2 are for car make and model, the 3rd is for car series. The goal is make a widget which lists car series' depending on current post (make and model).

function getCarListings() {

    global $post;
    //$post_id = $post->id;
    setup_postdata( $post );
    $post_id = get_the_ID();
    echo '<h2>' . $post_id  . '</h2>';

    $makeArray = get_the_terms($post_id, 'make'); //make taxonomy for current post
    //print_r($makeArray);
    $makeTag = $makeArray[0]->name;
    //print_r($makeTag );

    $modelArray = get_the_terms($post_id, 'model'); //model taxonomy for current post
    $modelTag = $modelArray[0]->name;


    //add_image_size( 'realty_widget_size', 85, 45, false );
    $mytaxomomies= array(
        // 'relation' => 'AND',
        array(
            'taxonomy' => 'make',
            'terms' => array( $makeTag ),
            'field'    => 'slug',
            'operator'=> 'AND',
        ),
        array(
            'taxonomy' => 'model',
            'terms' =>  array( $modelTag ),
            'field'    => 'slug',
            'operator'=> 'AND',
        )
    );

    $args = array(
        'post_type'=>'listings',
        'tax_query'=> $mytaxomomies,
    );
    $listings = new WP_Query($args);
    $term_array = [];
//  $listings->query('post_type=listings&posts_per_page=-1' );  
    if($listings->found_posts > 0) {

            while ($listings->have_posts()) {
                $post_get = get_the_ID();
                $term_get = get_the_terms($post_get, 'Car_Series');
                $term_array = $term_get;
                 print_r($term_get);
                array_push( $term_array, $term_get);

            }
        print_r($term_array);
        wp_reset_postdata(); 
    }else{
        echo '<p style="padding:25px;">No listing found</p>';
    }

 }

The top part gets the post id of the main page, which I am able to retrieve the car make and car Model. I then make a loop with these 2 taxonomies, trying to retrieve the 3rd taxonomy terms into an term_array. But it seems print_r($term_array) is blank but print_r($term_get) shows my WP object.

Why can I not retrieve collection of terms on that last array ($term_array)?

Answer 1

The loop for $listings should include a call to $listings->the_post() so that the global post object is assigned to the current listing in the loop:

        while ( $listings->have_posts() ) {
            /*** Add the following line: ***/
            $listings->the_post();

            $post_get = get_the_ID();
            $term_get = get_the_terms($post_get, 'Car_Series');
            $term_array = $term_get;
            print_r($term_get);
            array_push( $term_array, $term_get);
        }

Without this, functions that rely on the global post object, such as get_the_ID() will not return the expected results.