What is the performance difference in CodeIgniter?

Both approaches of passing the Codeigniter superobject as a parameter or using $CI =& get_instance() have their own considerations.

When passing the superobject as a parameter, you are directly injecting the dependency, which can make the code more modular and testable. It allows you to easily replace the superobject with a mock object during unit testing.

On the other hand, using $CI =& get_instance() within the function allows you to access the Codeigniter instance anywhere within the function, even if it's deeply nested. It provides more flexibility in accessing various resources and components of Codeigniter without explicitly passing them as parameters.

In terms of performance, the difference between the two approaches is generally negligible. However, using $CI =& get_instance() within the function may have a slightly higher overhead due to the function call and object assignment.

Ultimately, the choice between the two approaches depends on your specific needs and coding style preferences. If modularity and testability are important to you, passing the superobject as a parameter is recommended. If convenience and flexibility in accessing Codeigniter resources are more crucial, using $CI =& get_instance() can be a suitable approach.