laravel add amount to the next parent in loop - php

Question

I have a loop which will get the parent of a user but only up to the max user rank which is Senior.
My question is how to add the amount assigned to a user rank if he is not/skipped in the loop or no record found for that rank.
The code below is working and inserting the earnings to each rank, because the parents ranks are present in the database. But what if some is not, I want to add the amount of that user who is not in the loop-to the next rank.
Imagine that it is looping through the parent until it gets to Senior, that's how it works.
The rank are in order
Junior
Premium
Advanced
Senior
Ranks with their corresponding amount value
Junior - 100
Premium - 150
Advanced - 200
Senior - 250
Users table
+------+------------+-------------+------------+
| id | username | parent_id | rank |
+------+------------+-------------+------------+
| 1 | john | NULL | Senior |
| 2 | jane | 1 | Advanced |
| 3 | josh | 2 | Premium |
| 4 | joey | 3 | Junior |
| 5 | jade | 4 | Basic |
+----------------------------------------------+
Code
$user_id = 5; // jade
$parent_id = 4;
// call the function to insert the earnings
self::insertEarnings($user_id,$parent_id);
private function insertEarnings($user_id,$parent_id) {
if ($parent_id > 0) {
$user_parent = $parent_id;
$has_parent = true;
// start iteration
while($has_parent == true){
$account = User::where('id',$user_parent)->first();
$amount = 0;
if ($account->rank == "Junior" ) {
$amount = 100;
} elseif ($account->rank == "Premium") {
$amount = 150;
// for example this user/parent does not exist the amount(150) for him will be added to the next rank which is the Advance
} elseif ($account->rank == "Advanced") {
$amount = 200;
} elseif ($account->rank == "Senior") {
$amount = 250;
// set to false to stop the iteration
$has_parent = false;
}
$earnings = new Earnings;
$earnings->user_id = $account->id;
$earnings->amount = $amount;
$earnings->save();
$next_parent = User::where('id',$user_parent)->first();
$user_parent = $next_parent->parent_id;
if($user_parent == 0){
$has_parent = false;
}
}
}
}
Edit:
The $user_id is not used in this example, but there's a use to that that didn't included in the question because that is not the main problem.