PHP While loops making server time out

Question

I'm trying to make a simple PHP function to format when the user was last active. I've been awake for a while and the answer just isn't coming to me.

The database connects just fine.

Any idea why my while loops are timing out?

function showActiveUsers(){

$host_name = '#####';
$database = '#####';
$user_name = '#####';
$password = '#####';

$conn = new mysqli($host_name, $user_name, $password, $database);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

$sql = "SELECT * FROM user ORDER BY last_active DESC";
$result = $conn->query($sql);

$conn->close();

$ago = 0;
$d = 0;
$h = 0;
$m = 0;

foreach($result as $check)
{
    $ago = time()-$check["last_active"];

    if($ago<=120)
    {
        echo '<p>'.$check["username"].'<img width="10px" src="res/activedot.png"/></p>';
    }
    else
    {
        $d = 0;
        $h = 0;
        $m = 0;
        while($ago<=86400)
        {
            $d++;
            $ago = $ago-86400;
        }
        while($ago<=3600)
        {
            $h++;
            $ago = $ago-3600;
        }
        while($ago<=60)
        {
            $m++;
            $ago = $ago-60;
        }
    }

}


}

It's probably insanely simple and I've just been awake way too long.