如果找不到$ _GET，如何设置默认的Cookie进行推介？

Question

I want make a simple referral system. Basically referral URL structure something like this.

http://domain.com/?ref=abc
http://domain.com/about-us/?ref=abc
http://domain.com/slug/more-slug/?ref=abc

1. How do I validate if no cookie found, script will set default cookie to $_COOKIE['referral'] = 'generic'
2. If cookie already exists just keep it.

Here what I've done but it always replace to generic if no referral found although previously already having it.

if (!isset($_COOKIE['referral'])) {
    setcookie('referral', 'generic', time() + 31536000);
} else if (isset($_GET['ref']) && !empty($_GET['ref'])) {
    $ref = trim(secure($_GET['ref']));
    setcookie('referral', $ref, time() + 31536000);
}

Answer 1

if(!isset($_COOKIE['referral'])){
    if(isset($_GET['ref']) && !empty($_GET['ref'])) {
        $ref = trim(secure($_GET['ref']));
        setcookie('referral', $ref, time() + 31536000);
    }else{
        setcookie('referral', 'generic', time() + 31536000);
    }
}

you could remove isset($_GET['ref']) cause you check !empty($_GET['ref'])