Other Features: Introduction
In addition to the primary topics covered in this user guide, Hack has other noteworthy features that deserve attention.
- Constructor parameter promotion allows you to reduce class property boilerplate in your code.
- Trait and interface requirements allow you to restrict what classes can use a trait or implement an interface.
- Enhanced autoloading enhances the normal class autoloading process with the autoloading of Hack (and PHP) functions and constants, as well as Hack traits.
- Variadic functions allow functions to take a variable number of arguments. They are supported like in PHP, but must be explicitly marked variadic, enhancing type safety and checking.
- The placeholder variable
$_allows for variables of any type to be assigned to it with the agreement that the variable will not be used after assignment, such as when iterating over key/value pairs where you don't care about the value.