variables are case sensitive what about constants?

Answer 1

constant are also case sensitive you can make them case insensitive just by writing code as below
define("xyz", 24, false);
so that you can use xyz or XYZ by default the value is true...

Answer 2

constants are also case sensitive by default, but you can make them case insensitive.

Answer 3

constants are default case sensitive. but you can change this by passing "true" in define ()