functions.php

<?php

/**
 * AJAX Load More
 * @link http://www.billerickson.net/infinite-scroll-in-wordpress
 */
function be_ajax_load_more() {
  $data = 'Additional posts go here';
  wp_send_json_success( $data );
  wp_die();
}
add_action( 'wp_ajax_be_ajax_load_more', 'be_ajax_load_more' );
add_action( 'wp_ajax_nopriv_be_ajax_load_more', 'be_ajax_load_more' );