php - Cookies not working on my website, but work on localhost -

so, cookies aren't working on live version of website work on localhost (test) version. missing here?

setcookie('cookiename', $cookie, strtotime( '+365 days' ) ); 

here's code looks like. need declare cookie usage or that?

if(isset($_cookie['cookiename']) , $_cookie['cookiename'] != ""){    echo 'yes'; }else{    echo 'no'; } 

here's if statement returns yes on localhost no on live servers. they're in seperate files.

update: cookies work on chrome , opera, not safari , firefox.

try before setting cookie:

ini_set("session.cookie_domain", ".yourdomain.com");