IPN(3)

NAME
Business::PayPal::IPN - Perl extension that implements PayPal IPN v1.5

SYNOPSIS
  use Business::PayPal::IPN;

  my $ipn = new Business::PayPal::IPN() or die Business::PayPal::IPN->error();

  if ( $ipn->completed ) {
    # ...
  }

ABSTRACT
Business::PayPal::IPN implements PayPal IPN version 1.5. It validates transactions and gives you means to get notified of payments to your PayPal account. If you don't already know what PayPal IPN is this library may not be for you. Consult with respective manuals provided by PayPal.com, http://www.paypal.com/.

  WARNING
$Revision: 1.18 $ of Business::PayPal::IPN supports version 1.5 of the API. This was the latest version as of Tuesday, August 19, 2003. Supported version number is available in $Business::PayPal::IPN::SUPPORTEDV global variable. If PayPal introduces new response variables, Business::PayPal::IPN automatically supports those variables thanks to AUTOLOAD. For any further updates, you can contact me or send me a patch.

PAYPAL IPN OVERVIEW
As soon as you receive payment to your PayPal account, PayPal posts the transaction details to your specified URL, which you either configure in your PayPal preferences, or in your HTML forms' "notify_url" hidden field.

When the payment details are received from, supposedly, PayPal server, your application should check with the PayPal server to make sure it is indeed a valid transaction, and that PayPal is aware of it. This can be achieved by re-submitting the transaction details back to https://www.paypal.com/cgi-bin/webscr and check the integrity of the data.

If the transaction is valid, PayPal will respond to you with a single string "VERIFIED", and you can proceed safely. If the transaction is not valid, you will receive "INVALID", and you can log the request for further investigation.

So why this verification step is necessary? Because it is very easy for others to simulate a PayPal transaction. If you do not take this step, your program will be tricked into thinking it was a valid transaction, and may act the way you wouldn't want it to act. So you take extra step and check directly with PayPal and see if such a transaction really happened

Business::PayPal::IPN is the library which encapsulates all the above complexity into this compact form:

  my $ipn = new Business::PayPal::IPN() or die Business::PayPal::IPN->error();

  # if we come this far, we're guaranteed it was a valid transaction.
  if ( $ipn->completed() ) {
    # means the funds are already in our paypal account.

  } elsif ( $ipn->pending() ) {
    # the payment was made to your account, but its status is still pending
    # $ipn->pending() also returns the reason why it is so.

  } elsif ( $ipn->denied() ) {
    # the payment denied

  } elsif ( $ipn->failed() ) {
    # the payment failed

  }

PREREQUISITES

•   LWP - to make HTTP requests

•   Crypt::SSLeay - to enable LWP perform https (SSL) requests. If for any reason you are not able to install Crypt::SSLeay, you will need to update $Business::PayPal::IPN::GTW to proper, non-ssl URL.

METHODS

•   "new()" - constructor. Validates the transaction and returns IPN object. Optionally you may pass it query and ua options. query denotes the CGI object to be used. ua denotes the user agent object. If ua is missing, it will use LWP::UserAgent by default. If the transaction could not be validated, it will return undef and you should check the error() method for a more detailed error string:

      $ipn = new Business::PayPal::IPN() or die Business::PayPal::IPN->error();

•   "vars()" - returns all the returned PayPal variables and their respective values in the form of a hash.

      my %paypal = $ipn->vars();
      if ( $paypal{payment_status} eq 'Completed' ) {
        print "Payment was made successfully!";
      }

•   "query()" - can also be accessed via "cgi()" alias, returns respective query object

•   "response()" - returns HTTP::Response object, which is the response returned while verifying transaction through PayPal. You normally never need this method. In case you do for any reason, here it is.

•   "user_agent()" - returns user agent object used by the library to verify the transaction. Name of the agent is "Business::PayPal::IPN/#.# (libwww-perl/#.##)".

Business::PayPal::IPN supports all the variables supported by PayPal IPN independent of its version. To access the value of any variable, use the corresponding method name. For example, if you want to get the first name of the user who made the payment ('first_name' variable):

  my $fname = $ipn->first_name()

To get the transaction id ('txn_id' variable)

  my $txn = $ipn->txn_id()

To get payment type ('payment_type' variable)

  $type = $ipn->payment_type()

and so on. For the list of all the available variables, consult IPN Manual provided by PayPal Developer Network. You can find the link at the bottom of http://www.paypal.com.

In addition to the above scheme, the library also provides convenience methods such as:

•   "status()" - which is a shortcut to "payment_status()"

•   "completed()" - returns true if "payment_status" is "Completed".

•   "failed()" - returns true if "payment_status" is "Failed".

•   "pending()" - returns true if "payment_status" is "Pending". Return value is also the string that explains why the payment is pending.

•   "denied()" - returns true if "payment_status" is "Denied".

RETURN VALUES OF METHODS
Methods can return 1, 0 or undefined as well as any other true value. The distinction between 0 (which is false) and undefined (which is also false) is important:

  $ipn->completed eq undef and print "Not relevant for this transaction type";
  $ipn->completed == 1 and print "Transaction was completed";
  $ipn->completed == 0 and print "Transaction was NOT completed";

In other words, methods return undef indicating this variable is not relevant for this transaction type ("txn_type"). A good example for such transactions is "subscr_signup" transaction, that do not return any "payment_status" nor "txn_id" variables. Methods return 0 (zero) indicating failure. They return 1 (one) or any other true value indicating success.

DEBUGGING
If for any reason your PayPal IPN solutions don't work as expected, you have no other choice but debugging the process. Although it sounds complex, it really is not.All you need to do is get your IPN script to dump Business::PayPal::IPN object into a file and investigate to see what exactly is happening. For this reason, we provide "dump()" method which does just that:

•   "dump([$filename] [,$indent])" - for dumping Business::PayPal::IPN object. If used without any arguments, simply returns the object as Perl data structure. If filename is passed as the first argument, object is dumped into the file. The second argument, if present, should be a value between 1 and 3 to indicate how well indented the dump file should be. For debugging purposes, I believe 2 is enough, but go ahead and try out for yourself to compare differences.

  Note that the object is dumped only once to the same file. So after investigating the dump,
  you may need to remove the file or dump to another file instead.

Interpreting the dump file may seem tricky, since it is relatively big file. But you don't need to understand everything in it. Simply look for the attribute called "_PAYPAL_VARS". It is a hashref that keeps all the variables returned from PayPal server. These are also the methods that are available through Business::PayPal::IPN object.

You can also investigate the content of "response" attribute. It holds the HTTP::Response object. Look for the "_content" attribute of this object. This is what was returned from PayPal.com in response to your request. Ideally, this should hold "VERIFIED". "INVALID" is also explainable though :-).

Before you do any "dumping" around, include the following lines on top of your IPN script if you haven't done so already. This will ensure that when PayPal.com calls your IPN script, all the warnings and error messages, if any, will be saved in this file.

  use CGI::Carp 'carpout';
  BEGIN {
    open(LOG, '>>path/to/error.log') && carpout(\*LOG);
  }

VARIABLES
Following global variables are available:

•   $Business::PayPal::IPN::GTW - gateway url to PayPal's Web Script. Default is "https://www.paypal.com/cgi-bin/webscr", which you may not want to change. But it comes handy while testing your application through a PayPal simulator.

•   $Business::PayPal::IPN::SUPPORTEDV - supported version of PayPal's IPN API. Default value is "1.5". You can modify it before creating ipn object (as long as you know what you are doing. If not don't touch it!)

•   $Business::PayPal::IPN::VERSION - version of the library

AUTHOR
Sherzod B. Ruzmetov <sherzodr@cpan.org>

CREDITS
Following people contributed to this library with their patches and suggestions. It's very possible that list is not complete. Help me with it.

Brian Grossman
    Fixes in the source code. pathces/brian-grososman.

Thomas J Mather
    Documentation fixes. patches/thomas-mather.patch

COPYRIGHT AND LICENSE
Copyright 2003 by Sherzod B. Ruzmetov.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

THIS LIBRARY IS PROVIDED WITH THE USEFULNESS IN MIND, BUT WITHOUT EVEN IMPLIED GUARANTEE OF MERCHANTABILITY NOR FITNESS FOR A PARTICULAR PURPOSE. USE IT AT YOUR OWN RISK.

REVISION
$Revision: 1.18 $