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