Automatically Calculate based on input

RichGags · 09-20-2012, 03:42 AM

I have a form for credit card processing. Currently the form field that collects the amount based on the users input looks like...

Code:

<input type="text" name="chargetotal" value="">

When the form is submitted, it calls to a php script that includes $_POST["chargetotal"] and that amount it charged to the credit card.

I would like to add a text area that automatically calculates and adds 3% to the amount the user enters. This way they know the exact amount they will be charged.

I assume I can just multiply $_POST["chargetotal"] by *.03 before the script sends the amount to charge to the bank so this field does not actually have to be the one the next page uses. It could just be a visual.

How do I make a new text area that automatically updates while leaving "chargetotal" in tact so on submit, the php script picks up $_POST["chargetotal"] properly?

Thanks,
Rich

Old Pedant · 09-20-2012, 06:13 AM

Code:

<input type="text" name="chargetotal" value="" 
    onchange="this.form.grandtotal.value = ( 1.03 * ( isNaN(this.value) ? 0 : this.value ) ).toFixed(2);"
    />
...
Grand total (with credit card fee): <input name="grandtotal" readonly />

Now... If your "chargetotal" field is ITSELF the result of some JavaScript calculations, then the onchange won't work. You'll have to show us more code, in that case.

Philip M · 09-20-2012, 07:52 AM

As an aside, I will never do business with any firm that makes a charge for using a credit card. Nor will I pay a "booking fee". Or an "administration fee".

RichGags · 09-20-2012, 01:42 PM

Old Pedant, Thank you so much. Worked perfectly.

Philip M, do you buy gasoline? In my state (New York), there are 2 prices listed at the pump. Cash price and Credit price. Do you use a credit card or always pay cash? The fee is one thing and a cost of doing business, but a rewards card tacks on an additional 2%-3% to the merchant. I believe it is unfair for me, as a business man to have to pay for miles or whatever the reward may be.

Just my opinion but thank you so much for the coding help

Philip M · 09-20-2012, 03:50 PM

Quote:

Originally Posted by RichGags

Old Pedant, Thank you so much. Worked perfectly.

Philip M, do you buy gasoline? In my state (New York), there are 2 prices listed at the pump. Cash price and Credit price. Do you use a credit card or always pay cash? The fee is one thing and a cost of doing business, but a rewards card tacks on an additional 2%-3% to the merchant. I believe it is unfair for me, as a business man to have to pay for miles or whatever the reward may be.

Just my opinion but thank you so much for the coding help

I am not an American, but if any petrol station in the UK tried to charge a premium for using a credit card they would soon be out of business.

Old Pedant · 09-20-2012, 10:27 PM

It is a common practice here in the US for credit cards to "kick back" a percentage of all or some specific charges to the credit card holder. 1% is most typical, but some cards kick back more for some charges, quite often including petrol (gasoline) purchases.

So you do have to wonder at the logic of it all: The credit card processing company charges the gas (petrol) station 3% of the amount and then kicks back 1% to 2% to the credit card user as an incentive to use the card.

It's no wonder than some stations have switched to "cash price" and "credit price". Not their fault; the credit card companies have pushed them into it.