A constantis a variable with a value that cannot be changed by the script. Therefore, such a value must be assigned at the same time that the constant is created. PHP provides two methods for creating constants: the const modifier and the define function.
Const
The const modifier is used to create class constants. Unlike regular properties, class constants do not have an access level specified because they are always publicly visible. They also do not use the dollar sign parser token ($). The naming convention for constants is all uppercase, with underscores separating each word.
class MyCircle{const ...
