Abstract classes and methods in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an abstract class in PHP?

An abstract class in PHP is a class that cannot be instantiated on its own. It is meant to be a base class that other classes extend. It can contain abstract methods that must be implemented by child classes.

beginner

What is an abstract method?

An abstract method is a method declared in an abstract class without a body. Child classes must provide their own implementation of this method.

beginner

Can you create an object from an abstract class directly?

No, you cannot create an object directly from an abstract class. You must extend it with a child class and instantiate the child class instead.

intermediate

Why use abstract classes and methods?

Abstract classes and methods help define a common template for related classes. They enforce that certain methods are implemented in child classes, ensuring consistent behavior.

beginner

Example of declaring an abstract class with an abstract method in PHP?

Example:<br><pre>abstract class Animal {
  abstract public function makeSound();
}

class Dog extends Animal {
  public function makeSound() {
    echo "Woof!";
  }
}</pre>

Which keyword is used to declare an abstract class in PHP?

A static

B interface

C final

D abstract

The keyword abstract is used to declare an abstract class in PHP.

What happens if a child class does not implement an abstract method from its parent abstract class?

A PHP throws a fatal error

B The code runs without errors

C The child class will be abstract too

D The method is ignored

PHP throws a fatal error if a child class does not implement all abstract methods from its parent abstract class.

Can an abstract class contain non-abstract methods?

A Yes, it can contain both abstract and non-abstract methods

B No, all methods must be abstract

C Only static methods are allowed

D Only private methods are allowed

An abstract class can have both abstract methods (without body) and non-abstract methods (with body).

Which of these is true about abstract classes?

A They can be instantiated directly

B They cannot have properties

C They can implement interfaces

D They must have at least one abstract method

Abstract classes can implement interfaces. They cannot be instantiated directly, can have properties, and do not have to have abstract methods.

How do you declare an abstract method in PHP?

A function methodName() {}

B abstract public function methodName();

C public function methodName() {}

D static function methodName();

Abstract methods are declared with the keyword abstract and a visibility modifier like public and have no body, e.g., abstract public function methodName();.

Explain what an abstract class is and why you would use one in PHP.

Think about a blueprint that sets rules for other classes.

Describe how abstract methods work and what happens if a child class does not implement them.

Consider a promise that child classes must keep.