javascript не работает внутри функции functions.php

functions.php вот тут не работает ?><script>alert('test')</script><?php в чем проблема ?

 add_action('wp_ajax_filter', 'filter_func');
 add_action('wp_ajax_nopriv_filter', 'filter_func');
 function filter_func(){
?><script>alert('test')</script><?php
     $slug =  $_POST['slug'];
     $data = array(); //setting up an empty PHP array for the data to go into
     $features = array();
     $query = new WP_Query( array(
         'tax_query' => array(
             array(
                 'taxonomy' => 'item_category',
                 'field'    => 'slug',
                 'terms'    => $slug
             )
         )
     ) );
     $cords = array();
     $i = 0;
     while ( $query->have_posts() ) {
         $query->the_post();
         $cords[$i] = array('title' => get_the_title(), 'id' => get_the_ID(),'latitude' => get_post_meta(get_the_ID(),'latitude' ,1), 'longitude' => get_post_meta(get_the_ID(),'longitude',1 ));
         $i++;
     }
     foreach($cords as $key => $value) {
         $cat = get_the_terms($value['id'], 'item_category' );
         $features[] = array(
             'category'=>$cat[0]->name,
             'title' => $value['title'],
             'type' => 'Feature',
             'properties' => array(),
             'geometry' => array(
                 'type' => 'Point',
                 'coordinates' => array(
                     $value['latitude'],
                     $value['longitude'],
                 ),
             ),
         );
     }
     print_r($features);
 }

вызываю вот так

xhr.onload = function () {
  const serverResponse = document.getElementById("serverResponse");
  serverResponse.innerHTML = this.responseText;
};
xhr.open(
  "POST",
  "http://lom.lom/wp-admin/admin-ajax.php",
);
xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhr.send("action=filter&slug=lube");