Double-Order, One Charge (a bug in the PayPal IPN - Website Payments Standard?)

[ilikemike]

I am using Zen-Cart 1.3.8a (with announced fixes applied) plus a few add-ons, for downloadable products only (i.e. the delivery system is totally automated).

Every once in a while, I receive an order as "two orders". That is, the customer only ordered once, PayPal notifies me of a single payment, but Zen-Cart creates two orders, with successive order numbers.

This is very troubling because this problem does not occur consistently or with apparent circumstances and so it is very hard to troubleshoot or point at the source of the problem (PayPal? Zen-Cart? Web-Host? Hackers?)

Comparing the two orders, I found the following differences only (except for Invoice No. of course):

                 Invoice No. **1                    Invoice No. **2
                 ---------------                    ---------------
IP Address:      75.171.230.185 - 75.171.230.185    75.171.230.185 - 66.211.170.66
Address Country: US                                 
Trans. Type:     web_accept                         unique
Payment Date:    11/30/1999 00:00:00                01/08/2011 21:13:31                
Exchange Rate:   1.00                               0.00

Have you seen this problem before? Do you know what causes it? A possible fix?

[stevesh]

Haven't seen it, and don't know about a cause, but I suspect a switch to Paypal Express would possibly fix it.

[ilikemike]

Haven't seen it, and don't know about a cause, but I suspect a switch to Paypal Express would possibly fix it.

Hmmm... I prefer not to switch to PayPal Express as this implies monthly fees and with my very low sales volume I can't afford that for now.

In the meanwhile, I found a very similar problem description here. So it seems that it is a known problem, except that due to its nature it is being described differently by different people (that's why it was hard for me to find it).

DrByte suggests there to "try this fix". I am not afraid of modifying PHP files but then how do I verify that this is indeed the fix for the problem?

My hosting BTW is not Windows but Linux:

Server OS: Linux 2.6.34.6 (CentOS)
PHP Version: 5.2.15 (Zend: 2.2.0)
Database: MySQL 5.1.52
HTTP Server: Apache mod_fcgid/2.3.5 mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635

Additional tips and advice are most welcome. I hope that this will help many others experiencing the same problem.

Thanks.

[stevesh]

There are no monthly fees with Paypal Express. You're thinking of Paypal Payments Pro. Paypal Express is pretty much like Paypal Standard, only more secure and stable. There really isn't any reason to use Paypal Standard (IPN) any more.

[ilikemike]

There are no monthly fees with Paypal Express. You're thinking of Paypal Payments Pro. Paypal Express is pretty much like Paypal Standard, only more secure and stable. There really isn't any reason to use Paypal Standard (IPN) any more.

Oh, I may have been sleeping under a rock. Thanks for correcting my misconception about this. Do you happen to know whether Paypal Express allows purchases by customers who don't have a PayPal account? ("IPN - Website Payments Standard" does allow that)

[stevesh]

It didn't used to, but it does now.

[ilikemike]

It didn't used to, but it does now.

Perfect. Thanks so much.

BTW, "I suspect a switch to Paypal Express would possibly fix it" doesn't really encourage me to switch to PayPal Express.... but I will definitely try PayPal Express now that it allows customers who don't have a PayPal account to purchase with their credit card. Also, the prospect of an increase in conversion rate sounds promising (with the downside of possible increase in buyer's remorse).

[stevesh]

"Every once in a while, I receive an order as "two orders""

makes it difficult to offer more definitive advice, particularly with a problem I can't test a solution for. Switching to the much more stable Paypal Express seemed the most logical first thing to try.

[ilikemike]

makes it difficult to offer more definitive advice, particularly with a problem I can't test a solution for.

I agree as that's exactly what I wrote in the 3rd paragraph in my original post.

Switching to the much more stable Paypal Express seemed the most logical first thing to try.

Is it more stable because it has been tested by more people?

Theoretically, this problem could occur in Paypal Express as well, so it seems to me that the best way to test a solution is to let it be used for a long enough time (greater than 6 months) by as many people as possible. If no such problem is reported back, then we know it doesn't exist there. Unfortunately, I don't know a non-statistical test for a statistical problem like this, but if someone has an idea, this would be great.

[Tech-E]

I just experienced the same problem with a double order and single payment with PayPal. I've been using Zen Cart and PayPal for three years and this is the first time I've seen this problem. It looks like a PayPal problem with a double confirmation that created two orders.

What does it take to switch to PayPal Express?

Do I have to change anything with my PayPal account?