Simple logical calculations not working in PHP

Question

I have a scenerio that I want to achieve. Lets say there are 4 people A,B,C and D. Each user can deposit $10. And the deduction fee is $1. So initially we have

A: 10

Now when B will join, B will give $1 as deduction fee to the company and the company will share it in the previous clients. So.

A: 10+1
B: 9

Now person C joins in and the same thing happens. Now $1 deducted fee from C will be shared in A and B.

A: 10+1+0.5
B: 9+0.5
C: 9

There can be any n number of users and the starting free and deduction fee are variable. I am unable to do it successfully. This is my current code.

<?php

$i;
$y;
$people = 10;
$stake = 1;
$dev = 0.1;
$counter = 0;
$inner_counter = 0;
$total_money = $stake * $people;
$remaining = $total_money * $dev;
for ($y = $people; $y > 0; $y--) {
    echo "Total Deposit: " . $stake . " | Profit: ";
    $inner_counter = 0;
    for ($i = 0; $i < $y; $i++) {
        echo($stake * $dev);
        $counter++;
        $inner_counter++;
    }
    echo '<br>';
    echo " Inner:" . $inner_counter . "";
    echo '<br>';
}
echo $counter;
echo '<br>';
for ($x = 0; $x <= $people; $x++) {
    echo "($x / $counter)*$dev ";
    echo '<br>';
}

I am completely lost. If anyone can tell me a better approach, it'd help as well.

Answer 1

You can loop the count and foreach an array_slice to split the fee between the n number of people.

$people = ["A" => [], "B" => [], "C" => [], "D" => [], "E" => []];
$deposit = 10;
$fee =1;
$people["A"]["sum"] = $deposit;

for($i=1;$i<count($people);$i++){ // loop the same number of times as count of people
    foreach(array_slice($people,0,$i) as $key => $p){ // only loop the number of people that should share the fee
        if(!isset($people[$key]["sum"])) $people[$key]["sum"] = $deposit-$fee; // if it's the first round give them the starting sum
        $people[$key]["sum"] += $fee/$i; // give them the percentage
    }
}
$keys = array_keys($people);
$people[end($keys)]["sum"] = $deposit-$fee;
var_dump($people);

output:

array(5) {
  ["A"]=>
  array(1) {
    ["sum"]=>
    float(12.083333333333)
  }
  ["B"]=>
  array(1) {
    ["sum"]=>
    float(10.083333333333)
  }
  ["C"]=>
  array(1) {
    ["sum"]=>
    float(9.5833333333333)
  }
  ["D"]=>
  array(1) {
    ["sum"]=>
    float(9.25)
  }
  ["E"]=>
  array(1) {
    ["sum"]=>
    int(9)
  }
}

https://3v4l.org/fDEbL

Answer 2

Try this. I think the comments in the code and the variable names make it fairly self-explanatory:

$deposit = 10;
$fee = 1;
$people = 4;
$balances = array();
for ($p = 1; $p <= $people; $p++) {
    // person p makes a deposit
    $balances[$p] = $deposit;
    // if more than one person, divide the fee by the preceding despositors
    if ($p != 1) {
        $balances[$p] -= $fee;
        $split_fee = $fee / ($p - 1);
        for ($i = 1; $i < $p; $i++) {
            $balances[$i] += $split_fee;
        }
    }
}
print_r($balances);

Output: ($people = 4):

Array
(
    [1] => 11.833333333333
    [2] => 9.8333333333333
    [3] => 9.3333333333333
    [4] => 9
)

Output ($people = 10):

Array
(
    [1] => 12.828968253968
    [2] => 10.828968253968
    [3] => 10.328968253968
    [4] => 9.9956349206349
    [5] => 9.7456349206349
    [6] => 9.5456349206349
    [7] => 9.3789682539683
    [8] => 9.2361111111111
    [9] => 9.1111111111111
    [10] => 9
)

Edit

Based on OPs feedback, here is a version which takes an associative array as an input instead of a count of people, and populates that array with the final balances:

$deposit = 10;
$fee = 1;
$people =  [ 'A' => ['total' => 0],
             'B' => ['total' => 0],
             'C' => ['total' => 0],
             'D' => ['total' => 0], 
             'E' => ['total' => 0]
           ];
// get the names of the people
$names = array_keys($people);
for ($p = 1; $p <= count($people); $p++) {
    // person p makes a deposit
    $people[$names[$p-1]]['total'] = $deposit;
    // if more than one person, divide the fee by the preceding despositors
    if ($p != 1) {
        $people[$names[$p-1]]['total'] -= $fee;
        $split_fee = $fee / ($p - 1);
        for ($i = 1; $i < $p; $i++) {
            $people[$names[$i-1]]['total'] += $split_fee;
        }
    }
}
print_r($people);

Output:

Array
(
    [A] => Array
        (
            [total] => 12.083333333333
        )

    [B] => Array
        (
            [total] => 10.083333333333
        )

    [C] => Array
        (
            [total] => 9.5833333333333
        )

    [D] => Array
        (
            [total] => 9.25
        )

    [E] => Array
        (
            [total] => 9
        )

)