How to count downlines in Laravel?

$i = $_SESSION['ruserid'];// the list will show the downline for a member with id = 10
prin($i);// calling function prin
function prin($i) //definition
{
    $id = $i;
    // $q=mysql_query("select id from f2_users where up_id='$id'");
    $q = User::where('sponser_id', $i)->get();
    $count = count($q);// gives new value each time
    foreach ($q as $r) {
        $i = $r[0];
        echo $i;
        echo "<br>";
        prin($i); // recursion
    }
}

How to convert above php code in laravel controller to get downlines?

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via Chebli Mohamed