Class Constants

When to use

• The user needs a named, compile-time constant value bound to a class or interface.
• The user wants several classes to share the same constant values via an interface or base class.
• The user needs a fixed set of named values but targets PHP 7.4 or 8.0 where enums do not exist.

When NOT to use

• Do not model a closed set of related values with class constants when the runtime is PHP 8.1+ and an enum would fit.
• Do not use class constants for values that vary by environment or must change at runtime.

Core guidance