This syntax is used to access elements of an array -- see Arrays in the PHP manual.
Here, you are working with an associative array, called $config, that's contain at least two entries : business and different_text.
Considering the name of the $config variable, you have at least two advantages :
- related variables are grouped together in one variable -- easier to have them together
- only one variable (
$config) to work with
And, of course :
- You can add any number of configuration options without having to create a new variable : just add a new element to the
$config array.
That being said, of course, maybe the paypal API you are using is actually expecting some data passed as an associative array containing those elements -- if it is the case, you don't have much of a choice.