Mage_Catalog_Model_Product_TYPE::TYPE_CONFIGURABLE vs 'configurable'

Question

I'm working on an heavy customised magento version. Cancelling an order returned this fatal error:

Mage_Catalog_Model_Product_TYPE not found 

on this line code:

if($parent->getTypeId() == Mage_Catalog_Model_Product_TYPE::TYPE_CONFIGURABLE)

I fixed changing it to

if($parent->getTypeId() == 'configurable')

Can you please tell me what's the difference between them and if my solution can lead to other issues? many thanks

Answer 1

Mage_Catalog_Model_Product_Type::TYPE_CONFIGURABLE (notice the capitalization, which was the source of your error) is a constant. Using a constant for values that won't change is preferred over writing "magic strings"¹ all over the application.

Why?

• no errors due to typos. If you misspell the string, chances are, you won't notice until much later. If you reference a non existent constant, the compiler complains immediately (or with PHP, your IDE or static code analysis tools like CodeSniffer)
• easier to refactor
• more context, thus easier to understand. It is clear, where the value comes from and what purpose it serves

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^{1) Read this: https://stackoverflow.com/questions/47882/what-is-a-magic-number-and-why-is-it-bad - it is about magic numbers, but magic strings are almost as bad}

Answer 2

It should be Mage_Catalog_Model_Product_Type and not Mage_Catalog_Model_Product_TYPE (note the capitalisation on the last word)