php设置cookie,在js中如何获取

在php中设置cookie.

$email="[e-mail]";
setcookie("y_email",$email,time()+3600,"/");

js中获取cookie

function getCookie(c_name)
{
if (document.cookie.length>0)
  {
  c_start=document.cookie.indexOf(c_name + "=")
  if (c_start!=-1)
    { 
    c_start=c_start + c_name.length+1 
    c_end=document.cookie.indexOf(";",c_start)
    if (c_end==-1) c_end=document.cookie.length
    return unescape(document.cookie.substring(c_start,c_end))
    } 
  }
return "";
}

var y_email=getCookie('y_email');

php中让cookie失效

setcookie("y_email","",time()-3600,"/");