I’m a beginner in wordpress / php trying to learn. I want to use the update_post_meta function to populate one meta value (X) with another meta value (Y) everytime Y is changed. I did research and found a code that does this but it only updates the last published post. Can you help me how to modify the code so it works on every post?

    $args = array(
    'post_type' => 'listing',
    'post_status' => 'publish',
    'posts_per_page' => 1,
    'meta_key' => 'y'
);
$dbResult = new WP_Query($args);
global $post;
if ($dbResult->have_posts()) {
   $dbResult->the_post();

   $value = get_post_meta($post->ID,'y',true);
}

update_post_meta( $post->ID, 'x', $value) ; ?>