Interface declaration and implementation in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an interface in PHP?

An interface in PHP is a contract that defines methods a class must implement, without providing the method bodies.

beginner

How do you declare an interface in PHP?

Use the interface keyword followed by the interface name and method signatures inside curly braces.

beginner

What keyword is used by a class to implement an interface?

The <code>implements</code> keyword is used by a class to promise it will provide all methods defined in the interface.

intermediate

Can a class implement multiple interfaces in PHP?

Yes, a class can implement multiple interfaces by listing them separated by commas after the <code>implements</code> keyword.

intermediate

What happens if a class does not implement all methods of an interface?

PHP will throw a fatal error because the class breaks the contract defined by the interface.

Which keyword is used to declare an interface in PHP?

A class

B extends

C implements

D interface

The interface keyword declares an interface.

How does a class promise to follow an interface's contract?

A using the <code>extends</code> keyword

B using the <code>implements</code> keyword

C by defining the interface inside the class

D by calling interface methods directly

Classes use implements to promise to provide all interface methods.

Can an interface contain method bodies in PHP?

A Only if methods are static

B Yes, always

C No, never

D Only if methods are abstract

Interfaces only declare method signatures without bodies.

What happens if a class misses implementing a method from an interface?

A PHP throws a fatal error

B PHP ignores the missing method

C The class works but with warnings

D The interface is automatically updated

PHP requires all interface methods to be implemented; otherwise, it throws a fatal error.

How can a class implement multiple interfaces?

A List interfaces separated by commas after <code>implements</code>

B Use multiple <code>implements</code> keywords

C Use <code>extends</code> keyword

D Define interfaces inside the class

Multiple interfaces are listed separated by commas after implements.

Explain what an interface is in PHP and how a class uses it.

Think of an interface as a promise a class makes.

Describe what happens if a class does not implement all methods from an interface it declares to implement.

PHP is strict about interfaces.