substract with phpspreedshet - php

Question

I have a php front end for a database with expenses on a project.
I use phpspreadsheet to create reports from this database and until now everything worked great.
In the excel table I export three columns from the database table: type of expense, amount, date of expense.
The total amount for each type of expenses is entered in the table as a positive number and the quantities that are subtracted are entered as negative numbers - example: category of expense: travel costs, amount: 100, date | travel costs, amount: -10, date | travel costs, amount: -25, date, etc. In the excel template that I use with phpspreadsheet I created a fourth column 'balance'. In this column I substract the negative initial values from the starting amount that is positive and I end up with a excel table having four columns: travel costs, amount: 100, date, balance:100 | travel costs, amount: -10, date, balance:90 | travel costs, amount: -25, date, balance: 65 etc.
Until now it was simple because I knew the types of expenses - they were entered by me in the database so the users can only select between these predefined values and I got a sheet with multiple tables for each type of expense:
$sql="SELECT type_expense, , date, amount FROM expenses where acronym = '" . $_SESSION['idproject'] . "' ORDER BY type_expense";
$rsSql=db_query($sql,$conn);
$baseRow = 17;
$r=0;
$sum=0;
while ($data2 = db_fetch_array($rsSql)){
$row = $baseRow + $r;
$spreadsheet->getActiveSheet()->insertNewRowBefore($row, 1);
if($data2['type_expense']=='travel costs'){
$spreadsheet->getActiveSheet()->setCellValue('A' . $row, $r + 1)
->setCellValue('B' . $row, $data2['type_expense'])
->setCellValue('C' . $row, $data2['amount'])
->setCellValue('D' . $row, $data2['date']);
$sum=$sum+$data2['amount'];
$spreadsheet->getActiveSheet()->setCellValue('E'. $row , $sum);
$r= $r+1;
}
}
$spreadsheet->getActiveSheet()->removeRow($baseRow - 1, 1);
I use the same code for populating tables in the predefined sheet for the other two type of expenses: personnel cost and other expenses.
The problem is that now users need to define their own types of expenses so the code above could not work because I don't know how they define the type expense so I can use it in the if conditional inside the loop.
Also the sheet will be overcrowded with tables so I need to create a single table that define type of expense, date, amount and balance for all type of expenses - type of expense: travel costs, date, amount: 100, balance: 100 | type of expense: travel costs, date, amount: -10, balance: 90 | type of expense: personnel costs, amount: 10, date, balance:10 | type of expense: personnel costs, date, amount: -5, balance:5, etc
I tried with a conditional for all type of expenses as positive (this is the initial amount from where all the values are subtracted) but I get 0 in all the rows form the balance column.
I really need a suggestion where to go from here in order to have a single table with subtraction on each type of expenses.