[PHP] AJAX CORS verification

<?php
/**
 * Cors domain verify and detect AJAX.
 *
 * @todo only allow CORS request
 */
function cors($print_server = false)
{
  //header('Content-type: application/json; charset=utf-8');
  header('Access-Control-Allow-Origin: *'); //allow all AJAX REQUEST

  if (isset($_SERVER['HTTP_X_REQUESTED_WITH'])) {
    if ('xmlhttprequest' != strtolower($_SERVER['HTTP_X_REQUESTED_WITH'])) {
      return __LINE__ . false;
    } else {
      if (isset($_SERVER['HTTP_SEC_FETCH_SITE']) && isset($_SERVER['HTTP_SEC_FETCH_MODE']) && isset($_SERVER['HTTP_REFERER']) && isset($_SERVER['HTTP_ORIGIN']) && isset($_SERVER['HTTP_USER_AGENT'])) {
        $parseRef = parse_url($_SERVER['HTTP_REFERER']);
        $parseOri = parse_url($_SERVER['HTTP_ORIGIN']);
        if (!isset($parseOri['host']) || !isset($parseRef['host'])) {
          return __LINE__ . false;
        }
        if ($parseOri['host'] != $parseRef['host']) {
          return __LINE__ . false;
        }
        if ('same-origin' == $_SERVER['HTTP_SEC_FETCH_SITE'] && 'cors' == $_SERVER['HTTP_SEC_FETCH_MODE']) {
          return $parseOri['host'] == $parseRef['host'];
        } else {
          if ($print_server) {
            $_SERVER['PHP_LINE'] = __LINE__;

            return $_SERVER;
          } else {
            return false;
          }
        }
      }
    }
  }
  if (isset($_SERVER['HTTP_ORIGIN'])) {
    header('Access-Control-Allow-Origin: ' . $_SERVER['HTTP_ORIGIN']);
    header('Access-Control-Expose-Headers: date,content-type,transfer-encoding,connection,access-control-allow-origin,server,x-xss-protection,x-content-type-options,x-request-id,content-encoding,x-final-url');
    header('Access-Control-Allow-Credentials: true');
    header('Access-Control-Max-Age: 86400');    // cache for 1 day
    if (isset($_SERVER['HTTP_REFERER'])) {
      $parseRef = parse_url($_SERVER['HTTP_REFERER']);
      $parseOri = parse_url($_SERVER['HTTP_ORIGIN']);
      if (!isset($parseOri['host']) || !isset($parseRef['host'])) {
        return __LINE__ . false;
      }
      if ($parseOri['host'] != $parseRef['host']) {
        return __LINE__ . false;
      }
    } else {
      return __LINE__ . false;
    }
  }
  if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD'])) {
    // may also be using PUT, PATCH, HEAD etc
    header('Access-Control-Allow-Methods: GET, POST, OPTIONS');
  }

  if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS'])) {
    header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
  } else {
    header('Access-Control-Allow-Headers: X-Requested-With');
  }

  $final = isset($_SERVER['HTTP_ACCEPT']) && isset($_SERVER['HTTP_ORIGIN']) && isset($_SERVER['HTTP_REFERER']) && isset($_SERVER['HTTP_ACCEPT_ENCODING']) && isset($_SERVER['CONTENT_TYPE']) && isset($_SERVER['HTTP_ACCEPT_LANGUAGE']) && isset($_SERVER['HTTP_USER_AGENT']) && isset($_SERVER['UNIQUE_ID']);
  if (!$final && $print_server) {
    $_SERVER['PHP_LINE'] = __LINE__;

    return $_SERVER;
  }
  if ($final) {
    return true;
  }

  return false;
}