Picture the scene – all is going well, the site has launched and is happily taking orders just fine.. until.. one day, one order comes in strange and the packaging hasn’t been taken into account on the PayPal end. But it only happens once so you hope it was a glitch and move on.

Then it happens again, a few orders down the line.

You try to track the problem, but can’t recreate the error consistently.

Well… the problem and solution have been found! The error only seems to occur when a customer registers and uses PayPal standard – this causes PayPal to not take for the shipping, and so Magento sees the full amount hasn’t been taken for and doesn’t send an order confirmation. Very much less than ideal. We found the solution whilst browsing the Magento forum – you can see the original thread and solution as posted on the forum by clicking here.

The problem? Just five errant files:

• app/code/core/Mage/Paypal/Helper/Data.php
• app/code/core/Mage/Paypal/Model/Standard.php
• app/code/core/Mage/Paypal/Model/Api/Standard.php
• app/code/core/Mage/Paypal/Model/Api/Abstract.php

Now, you might think it would be as easy as just replacing those core files, but there is one important thing to remember: you should never edit core files. It’s a better practice to create local copies and one we recommend at ecommerce web design.

Step 1 – Open up your app/code folder, and create a new folder called “local”.

Step 2 – Duplicate the exact folder structure for the new files within the local folder, so the first file would be at app/code/local/Mage/PayPal/Model/Helper/Data.php

Step 3 – Upload your new local files. Bingo. Thanks for reading our latest Magento Blog!

Download the fixed PayPal files

In a Magento store it is possible to increase the current invoice ID to anything you like through phpMyAdmin. This is often something that needs doing when receieving the dreaded Paypal duplicate invoice ID error, which looks like this:

“The transaction was refused as a result of a duplicate invoice ID supplied.  Attempt with a new invoice ID”

A common cause of this error is having multiple Magento stores sharing the same Paypal account – as soon as Paypal recognises the same Invoice ID coming through, it sees this transaction as having been already processed and simply blocks it from happening at all. There are two solutions to this problem:

1. Use separate Paypal Accounts
2. Create a distance between the duplicate invoice IDs that means the current working one will never catch up to the other. (This way isn’t exactly the cleanest solution, and can only really work with small stores that won’t be making millions of orders in its lifetime).

First log in to phpMyAdmin and select the eav_entity_store table.

Check  and click ‘edit’ for the row that contains the field entity_type_id 18, which refers to invoice IDs. Here’s a key to each row:

entity_type_id 4 = order
entity_type_id 18 = invoice
entity_type_id 24 = shipment
entity_type_id 28 = credit memo

When opened, change the increment_last_id value to a number higher than the one currently set. In my example I have increased it to 100500531. See below:

Click on Go, and this will save the table with its new values.

Before this works however, you need to create a dummy order to get things going, Paypal still receives the old invoice ID as it stands. Simply process an order, perhaps using ‘Cheque / Money Order’, just to get it out the way quickly, then you can test a new Paypal payment which will now be using Invoice IDs starting from where you changed it.

This resolves the Paypal duplicate Invoice ID error.

An ocassional problem that arises when implementing Paypal Pro and Paypal Express into Magento is a security error that occurs during the checkout. While attempting to complete the order this message can be displayed:

“There was an error during communication with Paypal: Security error – Security header is not valid”

There are several reasons why this can happen, from not setting up an API request in your Paypal account to not entering the correct Paypal URL into the admin backend. However, one common cause is simply down to not entering your Paypal API credentials properly – even the slightest difference will cause the whole thing not to work. From Paypal you have to enter your:

• API Username
• API Password
• API Signature

Make sure that they are all copied and pasted perfectly, directly from the Paypal website, without any spaces either side of the code. Do not email or Skype the API credentials across as this can cause problems. Attempt this a couple of times if the error persists. It’s unlikely that there’s a problem with the Magento / Paypal code within your site. You can leave the Proxy Information, Debug Flag and Sandbox Flag left as they are when you set up Paypal Payments Pro.

For pretty much any e-commerce web design company setting up a new shop, the inclusion of PayPal is now considered highly important. PayPal was formed in March 2000 and has since achieved hug commercial success, largely attributed to its co-operation with eBay, which bought the firm in 2002. The UK alone is responsible for 20 million accounts. The reason for this substantial growth is largely down to it being the first to get there. By offering skeptical Internet users the opportunity to refrain from entering their credit card details on every site they wish to purchase from, they had provided a simple and safe payment system for anyone to use – and this resulted in a internationally-known, reliable brand.

However PayPal hasn’t been without it’s critics. There’s no doubting people’s disappointment with the charges made to the users when transactions are made, meaning sellers are not receiving the full amount for their sales. Users of PayPal are also the victims of unprecedented levels of phishing which have already cost unknowing users huge amounts of money. PayPal’s support system has also been largely criticized as their customer helpline is often very unresponsive, not to mention the unpredicatble freezing of accounts with no prior warning.

PayPal still seems like the most secure payment method available and I would urge all e-commerce sites to have it as an option alongside standard credit card transactions.