If the URL redirected and the new target is also redirected, we got the Locations in array. Also we got the HTTP codes in a number indexed values. 

Here a PART of the header (not all), how it is look like with this redirection chain ( the id=4 is the landing page):
/test.php?id=1 -> /test.php?id=2 -> /test.php?id=3 -> /test.php?id=4

array 
(
    [0] => HTTP/1.1 302 Moved Temporarily

    [Location] => Array
        (
            [0] => /test.php?id=2
            [1] => /test.php?id=3
            [2] => /test.php?id=4
        )

    [1] => HTTP/1.1 302 Moved Temporarily
    [2] => HTTP/1.1 302 Moved Temporarily
    [3] => HTTP/1.1 200 OK
)

In a typical situation we need only the landing page information, so here is a small code to get it:

$result = array();
$header = get_headers($url, 1);
foreach ($header as $key=>$value) {
    if (is_array($value)) {
        $value = end($value);
    }
    $result[$key] = $value;
}