What keyword is used to create an interface in PHP?

In PHP, the keyword used to create an interface is "interface." This keyword allows developers to define a contract that classes must adhere to if they implement the interface. An interface can contain method declarations, which means it defines the methods that a class must implement, but it does not provide any actual implementation for those methods.

Using interfaces promotes a design principle known as "programming to an interface, not an implementation," allowing for greater flexibility and the ability to swap out different implementations of functionality without changing the code that relies on the interface. Interfaces can also be used in multiple inheritance scenarios, as a class can implement multiple interfaces, enabling a more modular approach to defining functionality.

The other options serve different purposes. The "class" keyword is used to define a class, which is a blueprint for creating objects. "Abstract" is used to declare abstract classes that may have abstract methods, allowing for some methods to be defined and some to be left for subclasses. Lastly, "public" is an access modifier that determines the visibility of properties and methods, and is not related to the creation of interfaces.