Question

I am working on making my own custom CMS in PHP by hand and I have a few constants I have defined. Is there an easy way to modify the constants?

I was thinking about using something like fopen() and then changing it, but I have never used the filesystem functions.

Answer 1

A constant is an identifier (name) for a simple value. As the name
suggests, that value cannot change during the execution of the script
(except for magic constants, which aren’t actually constants). A
constant is case-sensitive by default. By convention, constant
identifiers are always uppercase.

The name of a constant follows the same rules as any label in PHP. A
valid constant name starts with a letter or underscore, followed by
any number of letters, numbers, or underscores. As a regular
expression, it would be expressed thusly:
[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*

From: Constants (PHP mamual)