如何在不重新加载页面的情况下获取最新的cookie ID？

Question

There is a page, that can be visited with one of three params: ref1, ref2 and ref3. Each time page script sets a couple of cookies to store ref-param and time of it's creation. After that it should find the latest one and be ready to deal with it. For example if I have "ref1" cookie as latest before visiting page and visit

script.php?ref2=1 

it should echo

latest is ref2

But it works properly (echoes right latest cookie) only after additional reloading of the page. What's wrong with this code?

if ($_GET['ref1']) {
    setcookie('ref1', 'ref1');
    setcookie('ref1_dt', time());
}

if ($_GET['ref2']) {
    setcookie('ref2', 'ref2');
    setcookie('ref2_dt', time());
}

if ($_GET['ref3']) {
    setcookie('ref3', 'ref3');
    setcookie('ref3_dt', time());
}

function getLatestCookie() {
    $refs = array(
        'ref1' => $_COOKIE['ref1_dt'],
        'ref2' => $_COOKIE['ref2_dt'],
        'ref3' => $_COOKIE['ref3_dt']
    );
    $maxs = array_keys($refs, max($refs));
    return $maxs[0];
}

$latest = getLatestCookie();
setcookie('latest', $latest, time() + 60 * 60 * 24 * 30, "/");
echo "latest is " . $latest;

Answer 1

As usual, reading docs was good enough. Cookies are available in $_COOKIE array after next page loading. So in my case I should assign $latest to GET-param value if it exists and else assign it with getLatestCookie().