Disallow variable overwrite in PHP

Question

Is it possible to prevent variables from being overwritten in PHP? I am making a system that has some reserved variables and I don't want them to be replaced with something else after a certain point. It is possible? If not, what can I do to approach something close to this?

Some of these vars are instantiated classes so I can't define them as constants.

Answer 1

Take a look at this question. Also the information about constants in the PHP manual may be helpful.

Answer 2

Yes, they're called constants.

If you cannot use them, assuming you're running the latest PHP version, you can use namespaces, using namespaces, you can have 2 variables of the same name, on different namespaces. So that you don't have collisions.