Price calculator integration with Paypal

**drtanz** · Jul 23, 2009 00:19

Hi I have made a price calculator which calculates the deposit due by players of my service, how can I link this to paypal so that I have a paypal 'Pay now' button that would open a page with correct amount passed in Euros and option to pay by credit card or paypal? Thanks

Frontend.php

Code:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script language="javascript" src="ajax.js"></script>
</head>

<body>
	<p style="display: inline;">Number of players:</p>
	<input type="text" id="num1" size="2">
	<input type="button" value=" = " onClick="doMath();">
	<div id="answer" style="display: inline; font-size: 16px"></div>
</body>
</html>

Ajax.php

Code:

http = getHTTPObject();
 
function getHTTPObject(){
  var xmlhttp;
 
  /*@cc_on
 
  @if (@_jscript_version >= 5)
    try {
      xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
    }catch(e){
      try{
      xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }catch(E){
      xmlhttp = false;
    }
  }
  @else
    xmlhttp = false;
  @end @*/
 
  if(!xmlhttp && typeof XMLHttpRequest != 'undefined'){
    try {
      xmlhttp = new XMLHttpRequest();
    }catch(e){
      xmlhttp = false;
    }
  }
 
  return xmlhttp;
}
 
function doMath(){
  var url = "backend.php?num1=" + document.getElementById('num1').value;
 
  http.open("GET", url, true);
  http.onreadystatechange = handleHttpResponse;
 
  http.send(null);
}
 
function handleHttpResponse(){
  if(http.readyState == 4){
    document.getElementById('answer').innerHTML = http.responseText;
  }
}

Backend.php

Code:

<?php
  if($_GET['num1']==""){
    echo "Please enter number of players";
    exit;
  }
 
  if(!is_numeric($_GET['num1'])){
    echo "Error: Invalid numbers.";
    exit;
  }
 
   echo $_GET['num1'] * 7;


?>

**Dan Grossman** · Jul 23, 2009 01:32

It's a bit complicated now, but you can go through the Pay Now button generator and uncheck the "host this button on PayPal" and every option that says something about encryption, to get a plain text link to a payment page. Then you can simply change the amount in the link to create a button for any amount.

Here's an example of how you might use that to create a page which redirects to PayPal with the appropriate amount. You'd link your 'buy' or 'checkout' button to that page:

PHP Code:


$purl = "https://www.paypal.com/cgi-bin/webscr?cmd=_ext-enter&redirect_cmd=_xclick&business=" . urlencode($YOUR_PAYPAL_EMAIL);
$purl .= "&item_name=" . urlencode($ITEM_DESCRIPTION);
$purl .= "&item_number=" . $YOUR_REFERENCE_NUMBER;
$purl .= "&currency_code=USD";
$purl .= "&amount=" . $AMOUNT
$purl .= "&shipping=0&tax=0";
$purl .= "&return=" . urlencode($YOUR_THANK_YOU_PAGE_URL);
$purl .= "&cancel_return=" . urlencode($PAGE_TO_GO_TO_UPON_CANCELLING);
$purl .= "&notify_url=" . urlencode($YOUR_IPN_PROCESSOR_URL);

//Redirect to PayPal
header("Location: $purl");

**drtanz** · Jul 23, 2009 01:42

With my script however the total amount is not stored as a variable, how can I change it to be able to pass it as a variable to paypal?

**Dan Grossman** · Jul 23, 2009 02:43

Sure it is. http.responseText is the amount to be paid, you could use that to construct your payment button.

But what you're doing is somewhat ridiculous. You don't need to make an asynchronous HTTP request to a backend PHP script to multiply a form input by 7. It's like calling up NASA and having them run your calculation through a supercomputer when you could just press the 7 button on the calculator in your hand. JavaScript could've done that client side on its own in one line.

I suggest simply having your form submit to a PHP page, normally, without AJAX, which multiplies the input by 7 and redirects to PayPal.

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