Unlike compiled languages, in PHP if you make a mistake, the program will crash when the line of code with the mistake is executed. When testing a PHP application, whether manually or automatically, developers spend a lot of their time discovering mistakes that wouldn’t even compile in other languages, leaving less time for testing actual business logic.
Enumerations, or Enums allow a developer to define a custom type that is limited to one of a discrete number of possible values. That can be especially helpful when defining a domain model, as it enables making invalid states unrepresentable. In other words, enums are a restricting layer on top of classes and class constants, intended to provide a way to define a closed set of possible values for a type.