Interface constants in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are interface constants in PHP?

Interface constants are fixed values defined inside an interface. They cannot be changed and are automatically public.

beginner

How do you define a constant inside a PHP interface?

Use the <code>const</code> keyword followed by the name and value, for example: <code>const STATUS = 'active';</code>

intermediate

Can interface constants be overridden in classes that implement the interface?

No, interface constants cannot be changed or overridden by implementing classes. They remain fixed as defined in the interface.

beginner

How do you access an interface constant from outside the interface?

Use the interface name followed by the scope resolution operator :: and the constant name, like InterfaceName::CONSTANT_NAME.

intermediate

Why use constants in interfaces instead of class constants?

Interface constants provide a way to define fixed values that all implementing classes share, ensuring consistency and avoiding duplication.

Which keyword is used to declare a constant inside a PHP interface?

A define

B var

C const

D static

Constants inside interfaces are declared using the const keyword.

Can a class that implements an interface change the value of an interface constant?

A Yes, anytime

B Only in the constructor

C Only if declared public

D No, interface constants are fixed

Interface constants are fixed and cannot be overridden or changed by implementing classes.

How do you access an interface constant named STATUS in interface UserInterface?

A UserInterface::STATUS

B UserInterface.STATUS

C $UserInterface::STATUS

D UserInterface->STATUS

Use the interface name followed by :: and the constant name to access it.

What visibility do interface constants have by default?

A public

B protected

C private

D package

Interface constants are always public and cannot have other visibility modifiers.

Why might you use constants in an interface?

A To store variable data

B To share fixed values across all implementing classes

C To allow classes to override values

D To create private data

Constants in interfaces provide fixed values that all implementing classes share for consistency.

Explain what interface constants are and how they are used in PHP.

Think about fixed values shared by all classes implementing the interface.

Describe how to access and why to use constants defined in an interface.

Consider the benefit of having common values for all implementers.