[RESOLVED] Cal with php

[spiritssight]

Hello all,

I am wondering how can I do some math using PHP, I want to be able to take the following and do it with php

person comes along and enters 10.00 now I want to come up with the answer of:

var are being passed to a func called donation_cal()

10.00 * 2.9% + 0.30 =

the func passes either the donation plus the fee or it give just the donation amount then once the person clicks next this is passed to paypal, I just not sure how to handle math

I think its like

$total_donation = math($donation * $fee)+ $flat_fee

please help thanks
Christopher

[zabmilenko]

You may be trying to do more than you need to:

donation: $10.00
fee: 2.9% + $0.30

total_billed_to_customer = 10.00
paypal_fee = total_billed_to_customer * 0.029 + 0.30
final_donation = total_billed_to_customer - paypal_fee

Something like that? This isn't code, just logic. I am trying to make sure I understand your problem.

[spiritssight]

zabmilenko wrote:

You may be trying to do more than you need to:

donation: $10.00
fee: 2.9% + $0.30

total_billed_to_customer = 10.00
paypal_fee = total_billed_to_customer * 0.029 + 0.30
final_donation = total_billed_to_customer - paypal_fee

Something like that? This isn't code, just logic. I am trying to make sure I understand your problem.

Ok, lets see if I can explain a little better:

person comes to site, enters donation amount or selects preset amounts
then person select to include the fee into there donation or not by check a check box

script checks to see how much the donation is then it see if the person going include the fees with there donation if so then it needs to do the math

if box check then do math
do math
else
no math needed

send person to conferm donation amount and if donating the fee also click submit and then it brings them to paypal / ask them for there information, that is not decided on yet

Thanks alot for your help

[bradgrafelman]

If you're asking about the math, you essentially had it right...

$donation = 10;
$fee = .029;
$fixed_cost = .3;

$total_amount = $donation * $fee + $fixed_cost;

You could also use [man]number_format/man to round the number to two decimal places (as money amounts usually are).

[spiritssight]

So the code that I have below would be right? the person is entering in dollar amount only no cents, is there a way to make this better or cleaner?

Thanks
Christopher

$donation = 10
$donate_process_fee = "yes"

<?php
function Donation_Cal($donation, $donate_process_fee)
  {
  $fee = .029
  $flat_fee = .3

if ( $donate_process_fee == "yes" ) 
	{
	$total_donation = $donation * $fee + $flat_fee;
	}  
else
	{
	$total_donation = $donation;
	}
  };

Donation_Cal();
?>

[laserlight]

So the code that I have below would be right? the person is entering in dollar amount only no cents, is there a way to make this better or cleaner?

Well, the function has no net effect as it does not return anything and has no side effects.

I suggest writing it as:

function Donation_Cal($donation, $donate_process_fee)
{
    if ($donate_process_fee == "yes")
    {
        $fee = .029;
        $flat_fee = .3;
        $donation = $donation * $fee + $flat_fee;
    }

return $donation;
}

Alternatively:

function Donation_Cal(&$donation, $donate_process_fee)
{
    if ($donate_process_fee == "yes")
    {
        $fee = .029;
        $flat_fee = .3;
        $donation = $donation * $fee + $flat_fee;
    }
}

[spiritssight]

What do you think, do I have it right now :-) ? Code is below.

Thanks again for the help!

Sincerely,
Christopher

$donation = 10.00
$donate_fee = "yes"

<?php

function Donation_Cal($donation, $donate_fee)
  {
  $fee = .0129  // var for processing fee
  $flat_fee = .3 // var for flat fee 

if ( $donate_fee == "yes" )  // checks to see if the value is Yes if yes then does the math if not sets the total_donation to amount with out fee
	{
	$total_donation = $donation * $fee * $fee + $flat_fee + $donation;
	}
else
	{
	$total_donation = $donation;
	}

return $total_donation;  // gives the answer to with or with out the yes checked
	};
?>

[laserlight]

What do you think, do I have it right now

Better, but you obviously did not test it since it has syntax errors. I suggest that you make your indentation more consistent.

[spiritssight]

Ok, I figured it out, I forgot to put a ; after the set var stuff. now it is not displaying any out put on the screen. any help would be great thanks alot folks

code below

Sincerely,
Christopher

<?php

$donation = 10.00;
$donate_fee = "yes";

function Donation_Cal($donation, $donate_fee)
  {
  $fee = .0129;
  $flat_fee = .3;

if ( $donate_fee == "yes" )
	{
	$total_donation = $donation * $fee * $fee + $flat_fee + $donation;
	}
else
	{
	$total_donation = $donation;
	}
};
return $total_donation;
?>

[spiritssight]

Ok, I got it to display now and every thing is good BUT one thing which is driving me nuts now as I have done the math and know what the correct answer is so here goes,

the code below gives a answer of when displayed:
Your total donation is:15.30249615

the code should be giving the answer of:
Your total donation is:15.549615

Whats going on here this is strage, if you take 1.29% / 100 it gives you 0.0129 which is what the computer I guess needs to be able to do the math

<?php

function Donation_Cal($donation, $donate_fee = "yes")
  {
  $fee = 0.0129;
  $flat_fee = .30;

if ( $donate_fee == "yes" )
	{
	$total_donation = $donation * $fee * $fee + $flat_fee + $donation;
	}					// 15.549615 = 15  * .0129 * .0129 + .3 + 15
else
	{
	$total_donation = $donation;
	}

return $total_donation;

};
echo "Your total donation is:" . Donation_Cal(15) ;
?>

[laserlight]

the code below gives a answer of when displayed:
Your total donation is:15.30249615

the code should be giving the answer of:
Your total donation is:15.549615

Eh, but (15 0.0129 0.0129) + 0.3 + 15 = 15.3 (3 s.f.)

[spiritssight]

laserlight wrote:

Eh, but (15 0.0129 0.0129) + 0.3 + 15 = 15.3 (3 s.f.)

I am not understand this! are you sayng this is right?

If so then why when I put in to a calculator program in windows and I get these answers:

15.00 1.29% = 0.1935 or 15 0.0129 = 0.1935
0.1935 * 0.0129 = 0.00249615
15 + 0.1935 + 0.00249615 = 15.19599615
15.19599615 + .3 = 15.49599615

So why is the app doing the wrong answer?

Also how can I get this to round up so that these numbers are in xx.xx format? I would like as close if not a penny more then what it should be, when the person check the box that says include processing fee we want it to cover the whole fee not most or more but exact now I don't think we will get exact so a penny more is ok

Thanks you for your help!

Sincerely,
Christopher

[laserlight]

15 + 0.1935 + 0.00249615 = 15.19599615

Where did this step come from? According to what you programmed, it should be:
15 0.0129 = 0.1935
0.1935 0.0129 = 0.00249615
0.00249615 + 0.3 = 0.30249615
0.30249615 + 15 = 15.30249615 = 15.3 (3 s.f.)

So why is the app doing the wrong answer?

Because you did not program the correct formula. Alternatively, you programmed the correct formula, but your own calculation is wrong.

Also how can I get this to round up so that these numbers are in xx.xx format?

Use [man]round/man. However, note that your calculations are in floating point. Where money is concerned, floating point inaccuracy can be a concern, so often calculations are done with integers (e.g., calculate based on number of cents instead of number of dollars) or fixed point arithmetic.

[spiritssight]

Hello,

I posted this also in another section and posting it here as it fixed the issue I was having. But any advice on making it better would be greatful

Also if you can look at how I am handleing the money put and give a better why would be great for the rounding and so on

<?php

$f_name = $_POST["f_name"];
$m_initial = $_POST["m_initial"];
$l_name = $_POST["l_name"];
$donation = $_POST["donation"];
$donation_fee = $_POST["donation_fee"];

function Donation_Cal($donation, $donate_fee)
  {
  $fee = 0.029;
  $flat_fee = .30;

if(isset($_POST["donate_fee"]))
    {
    $total_donation = $donation * $fee + $flat_fee + $donation + .01;
    }                    // 15.549615 = 15  * .0129 + .3 + 15
  else
      {
      $total_donation = $donation;
      }

$total_donation = round($total_donation, 2);
$total_donation = number_format($total_donation, 2);
return $total_donation;

};

echo "<b>Your name is:<b /> ". $f_name ." ". $m_initial . " " . $l_name . "," ;
echo " your total donation is: $" . Donation_Cal($donation, $donate_fee) ;

$donation = Donation_Cal($donation, $donate_fee);

echo '
<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="business" value="[e-mail]">
<input type="hidden" name="undefined_quantity" value="0">
<input type="hidden" name="item_name" value="Disability-Info-Seek.com Project Donation">
<input type="hidden" name="item_number" value="DIS-2008">
<input type="hidden" name="amount" value="'.$donation.'">
<input type="hidden" name="no_shipping" value="1">
<input type="hidden" name="no_note" value="1">
<input type="hidden" name="return" value="http://success">
<input type="hidden" name="cancel_return" value="http://cancel">
<input name="submit" type="submit" value="click here">
</form>

'
?>