Better Capture to Session Affiliate Id from GET in PHP

affiliate id to php session

[jhaurawachsman]

Can someone help me clean this up and make it more logical? I'm fried right now and can't seem to get a good line of code written :)

I'm trying to capture affiliate id from urls like ?aid=3056677. The idea is IF aff id is set in GET that takes precedence, the session and finally cookie with least. Also, we don't want to set an aff id that does not exist.

Do you know of a more tried and true method of doing this?

session_start(); // start session

// affiliate id
$g_aid = (isset($_GET['aid']) && $_GET['aid'] != '') ? trim($_GET['aid']) : false;
$s_aid = (isset($_SESSION['aid']) && $_SESSION['aid'] != '') ? trim($_SESSION['aid']) : false;
$c_aid = (isset($_COOKIE['aid']) && $_COOKIE['aid'] != '') ? trim($_COOKIE['aid']) : false;

if($g_aid !== false) // use get if set
$aid = $g_aid;
elseif($s_aid !== false) // next use session if get not set
$aid = $s_aid;
elseif($c_aid !== false) // cookie
$aid = $c_aid;
else
$aid = ''; // leave it empty

// if $aid is set is it in the $affiliates array?
//If not use the first key from that array
$aid = (isset($affiliates[$aid])) ? $aid : key($affiliates);

// save it and set it
// (maybe shouldn't be done if already stored?
setcookie('aid', $aid);
$_SESSION['aid'] = $aid;

[vincevincevince]

The only line which may be wrong, so far as I can see, is this:

$aid = (isset($affiliates[$aid])) ? $aid : key($affiliates);