Cookies: Guardar localstorage en cookies

function setCookieLSG(name,value,days) {
   var expires = "";
   if (days) {
     var date = new Date();
      date.setTime(date.getTime() + (days*24*60*60*1000));
      expires = "; expires=" + date.toUTCString();
   }
   document.cookie = name + "=" + (value || "") + expires + "; path=/";
}

localStorage.loquesea = 1;
setCookieLSG('loquesea', '1', 700);

Y luego en el PHP:
if (!isset($_COOKIE["loquesea"])) {
   ...
}