Arithmatic problem with percentages

[dcjones]

Hi all,

I have a problem trying to code the following script.

I have some vars which gets thier data from a MySQL table.
$row_pin_sales['saleprice'] // this var holds currency
$_SESSION'agentrate'] // this var hold a percentage, in the data table it is 33.3%
$row_pin_sales['discount'] // this var hold another percentage which can any amount under 33.3 %
$row_pin_sales['used_count'] // this var holds a number, lets say 2

$row_pin_sales['saleprice']; 
$_SESSION'agentrate'];
$row_pin_sales['discount'] ;
$row_pin_sales['used_count'];

if ($row_pin_sales['used_count'] > 0) {
echo money_format('%i',$agentcomm = $row_pin_sales['saleprice'] - $_SESSION'agentrate'] - $row_pin_sales['discount']);
} else {
echo "0.00";
}

What I am trying to do is display a result of:

$saleprice minus $_SESSION'agentrate'] minus $row_pin_sales['discount'].

I think my question is how do I deal with the vars that hold percentages when it come to constructing my code.

I hope I have provided enough information and written it clearly.

Help is required, please

[sheephat]

$SESSION'agentrate'] should this not be $SESSION['agentrate'] ?

i dont know with session but this is what flashed up in my head

[paulnaj]

Hi,

If you are applying both the agent rate AND the discount rate additively then ...

<?php
$final_price = floor(100 * $row_pin_sales['saleprice'] * (100 - $_SESSION['agentrate'] - $row_pin_sales['discount']))/100;
?>

But, you may want to apply the compound discount and agent rates, in which case ...

<?php
$final_price = floor(100 * $row_pin_sales['saleprice'] * (100 - $_SESSION['agentrate']) * (100 - $row_pin_sales['discount']))/100;
?>

Paul.

[dcjones]

Hi Paul and thanks for your swift reply.

I have used both the scripts and the both return zero(0)

am I doing something wrong here?

$final_price = floor(100 * $row_pin_sales['saleprice'] * (100 - $_SESSION['agentrate'] - $row_pin_sales['discount']))/100;

and

$final_price = floor(100 * $row_pin_sales['saleprice'] * (100 - $_SESSION['agentrate']) * (100 - $row_pin_sales['discount']))/100; 

[paulnaj]

Hi, oops forgot to divide the rate by 100 to get a fraction.

And just to make sure I understood how your variables are actually stored I've put it in a few steps this time ...

<?php
// Suppose ...
// $_SESSION['agentrate'] = 33.3
// $row_pin_sales['discount'] = 25 (say)

$rate = (100 - $_SESSION['agentrate'] - $row_pin_sales['discount'])/100;
// $rate = 0.417

$final_price = floor(100 * $row_pin_sales['saleprice'] * $rate)/100;
?>

Paul.

[dcjones]

Hi paul, sorry to be a pain on a Sunday afternoon.

// Suppose ...
// $_SESSION['agentrate'] = 33.3
// $row_pin_sales['discount'] = 25 (say)

$rate = (100 - $_SESSION['agentrate'] - $row_pin_sales['discount'])/100;
// $rate = 0.417

$final_price = floor(100 * $row_pin_sales['saleprice'] * $rate)/100; 

If I echo out $rate I get 0.667
and if I echo out $final_price I get 0

Again sorry to be a pain.
Many thanks

[paulnaj]

OK,

Just echo out all of ...

$_SESSION['agentrate']
$row_pin_sales['discount']
$row_pin_sales['saleprice']

... so I can see how your variables are stored.

P.

[dcjones]

Hi Paul
Sorry for the delay, I have been trying to get it to work, with no luck

$row_pin_sales['discount'] echo's 15 %

$_SESSION['agentrate'] echo's 33.3%

$row_pin_sales['saleprice'] echo's 12

I hope this helps

[paulnaj]

Hi again,

$row_pin_sales['discount'] echo's 15 %

Do you mean '15' or literally '15 %'.
It makes a difference ... 15 is numeric but '15 %' is a string of characters not suited to numerical calculations.

P

[dcjones]

Hi Paul

The data type are:

$row_pin_sales['discount'] | data type - VARCHAR | echo's 15 %
This hold a string of "15 %".

$_SESSION['agentrate'] | data type - VARCHAR | echo's 33.3%

$row_pin_sales['saleprice'] | data type - VARCHAR | echo's 12

Many thanks for your help

[paulnaj]

Hi again

First chance I've had to get back to your problem.

OK, you're using VARCHAR field types for numerical values. I would suggest that you update these to numerical field types.

Have a read about mysql data types. I would suggest DECIMAL 10,2 as the correct type for three fields we've talked about.

If you use phpMyAdmin to build db's then it's pretty straightforward to change data types although before you make any alterations, make sure you backup your existing tables as they are now. Just had to stress that!!

Paul.