Do unused use statements decrease performance?

Question

I want to know if unused use statements in my class affect performance of my php website?

Does php include all classes in beginning or when need it? If second choice then I think it doesn't affect performance of my system.

For Example: Use statement 'DbConnector' is not used

use model\adapter\DbConnector;

Answer 1

No, the use statement does not provoke the the class be loaded (it does not even trigger an autoloader).

It just declares a short name for a class. I assume the cost in terms of CPU and RAM is in the order of a few CPU cycles and a few bytes.