<?php

add_action('wp_ajax_some_ajax_generate_preview', 'some_ajax_generate_preview');
function some_ajax_generate_preview() {

$shortcode = $_REQUEST['shortcode'];
$clean_shortcode = some_ajax_clean_shortcode($_REQUEST['shortcode']);
$type = $_REQUEST['type'];
$post_types = get_option('some_ajax_types');

$response =  function ($status, $message) {

  return json_encode(['status' => $status,
                      'message' => $message]);

}

if(!current_user_can('administrator')) {

  echo $response(false, _('Some message!', 'text-domain'));
  die();

}

if(!in_array($type, $post_types)) {

  echo $response(false, _('Some message!', 'text-domain'));
  die();

}

if(!shortcode_exists($clean_shortcode)) {

  echo $response(false, _('Some message!', 'text-domain'));
  die();

}

echo $response(true, _('Some message!', 'text-domain'));
die();
}