Extending classes in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to make class B inherit from class A.

PHP

<?php
class A {
    public function greet() {
        return "Hello from A";
    }
}

class B [1] A {
}

$b = new B();
echo $b->greet();
?>

Drag options to blanks, or click blank then click option'

Aextends

Bimplements

Cinherits

Duses

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'implements' which is for interfaces, not classes.

Using 'inherits' which is not a PHP keyword.

Using 'uses' which is for traits.

In PHP, to make one class inherit from another, use the extends keyword.

2fill in blank

medium

Complete the code to call the parent class constructor inside the child class constructor.

PHP

<?php
class ParentClass {
    public function __construct() {
        echo "Parent constructor called\n";
    }
}

class ChildClass extends ParentClass {
    public function __construct() {
        [1];
        echo "Child constructor called\n";
    }
}

new ChildClass();
?>

Drag options to blanks, or click blank then click option'

Aparent::__construct()

Bself::__construct()

CChildClass::__construct()

Dthis->__construct()

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'self::__construct()' which calls the current class constructor and causes recursion.

Using 'this->__construct()' which is invalid syntax in PHP.

Calling the child class constructor inside itself causing infinite loop.

To call the parent class constructor in PHP, use parent::__construct().

3fill in blank

hard

Fix the error in the code to properly override the greet method and call the parent greet method.

PHP

<?php
class Base {
    public function greet() {
        return "Hello from Base";
    }
}

class Derived extends Base {
    public function greet() {
        return [1] . " and Derived";
    }
}

$d = new Derived();
echo $d->greet();
?>

Drag options to blanks, or click blank then click option'

ABase::greet()

B$this->greet()

Cparent->greet()

Dparent::greet()

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'parent->greet()' which is invalid syntax.

Using '$this->greet()' which calls the current method recursively.

Using 'Base::greet()' which requires static context or an instance.

To call a parent class method in PHP, use parent::methodName().

4fill in blank

hard

Fill both blanks to create a child class that overrides a method and calls the parent method inside it.

PHP

<?php
class Animal {
    public function sound() {
        return "Some sound";
    }
}

class Dog [1] Animal {
    public function sound() {
        return [2] . " Woof!";
    }
}

$dog = new Dog();
echo $dog->sound();
?>

Drag options to blanks, or click blank then click option'

Aextends

Bimplements

Cparent::sound()

Dself::sound()

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'implements' instead of 'extends' for class inheritance.

Using 'self::sound()' which calls the current class method and causes recursion.

The child class uses extends to inherit. Inside the overridden method, parent::sound() calls the parent's method.

5fill in blank

hard

Fill all three blanks to define a child class that extends a parent, overrides a method, and calls the parent's method with additional text.

PHP

<?php
class Vehicle {
    public function description() {
        return "This is a vehicle";
    }
}

class Car [1] Vehicle {
    public function description() {
        return [2] . [3];
    }
}

$car = new Car();
echo $car->description();
?>

Drag options to blanks, or click blank then click option'

Aextends

Bparent::description()

C " and it has 4 wheels"

Dself::description()

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'self::description()' which calls the current method recursively.

Not using 'extends' for inheritance.

Forgetting to concatenate the strings properly.

The class uses extends to inherit. The method calls parent::description() and adds extra text.