//FUNCTIONS PHP

// Enqueue script
function ajax_filter_posts_scripts() {
  // Enqueue script
  wp_register_script('afp_script', get_template_directory_uri() . '/js/ajax-filter-posts.js', false, null, false);
  wp_enqueue_script('afp_script');

  wp_localize_script( 'afp_script', 'afp_vars', array(
        'afp_nonce' => wp_create_nonce( 'afp_nonce' ), // Create nonce which we later will use to verify AJAX request
        'afp_ajax_url' => admin_url( 'admin-ajax.php' ),
      )
  );
}
add_action('wp_enqueue_scripts', 'ajax_filter_posts_scripts', 100);

$result = array();

// Script for getting posts
function ajax_filter_get_posts( $taxonomy ) {

  // Verify nonce
  if( !isset( $_POST['afp_nonce'] ) || !wp_verify_nonce( $_POST['afp_nonce'], 'afp_nonce' ) )
    die('Permission denied');

  $taxonomy = $_POST['taxonomy'];

  // WP Query
  $args = array(
    'tag'            => $taxonomy,
    'post_type'      => 'post',
    'posts_per_page' => -1,
  );

  // If taxonomy is not set, remove key from array and get all posts
  if( !$taxonomy ) {
    unset( $args['tag'] );
  }

  $query = new WP_Query( $args );

  if ( $query->have_posts() ) : while ( $query->have_posts() ) : $query->the_post();

    $result['response'][] = '<h2><a href="'.get_permalink().'">'. get_the_title().'</a></h2>' . get_the_excerpt();
    $result['status']     = 'success';

  endwhile; else:
    $result['response'] = '<h2>No posts found</h2>';
    $result['status']   = '404';
  endif;

  $result = json_encode($result);
  echo $result;

  die();
}

add_action('wp_ajax_filter_posts', 'ajax_filter_get_posts');
add_action('wp_ajax_nopriv_filter_posts', 'ajax_filter_get_posts');


//TAG.PHP

 <?php get_header(); ?>

<div class="row">

    <div class="col-md-16">

  		<div class="col-md-4 col-md-offset-1">

            <h1 class="entry-title"><?php _e( 'Tag Archives: ', 'blankslate' ); ?><?php single_tag_title(); ?></h1>

				<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>

                    <?php ajax_filter_get_posts (); ?>

                    <div class="tagged-posts"></div>

                <?php endwhile; endif; ?>

		</div>

    </div>

</div>

<?php get_footer(); ?>