Types
PHP Manual

Value types

Value types are those which not only check the type of a value but also the value itself. PHP has support for two value types: false as of PHP 8.0.0, and true as of PHP 8.2.0.

Warning

Prior to PHP 8.2.0 the false type could only be used as part of a union type.

Note: It is not possible to define custom value types. Consider using an enumerations instead.