Method overriding in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of method overriding with parent call

What is the output of this PHP code when run?

PHP

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

class Dog extends Animal {
    public function sound() {
        return "Bark";
    }
}

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

A Error: Cannot override method

B Some sound

C Bark

D No output

💡 Hint

Look at which class's method is called when you create a Dog object.

The Dog class overrides the sound method of Animal. When calling $dog->sound(), the overridden method in Dog runs, returning "Bark".

❓ Predict Output

intermediate

Output when calling parent method inside overridden method

What will this PHP code output?

PHP

<?php
class Vehicle {
    public function start() {
        return "Vehicle started";
    }
}

class Car extends Vehicle {
    public function start() {
        return parent::start() . " and Car ready";
    }
}

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

A Fatal error: Cannot access parent method

B Car ready

C Vehicle started

D Vehicle started and Car ready

💡 Hint

The overridden method calls the parent method and adds extra text.

The Car class overrides start() but calls parent::start() to get the base message, then adds " and Car ready". So the output is combined.

🔧 Debug

advanced

Identify the error in method overriding

What error will this PHP code produce when run?

PHP

<?php
class Base {
    private function show() {
        echo "Base show";
    }
}

class Child extends Base {
    public function show() {
        echo "Child show";
    }
}

$obj = new Child();
$obj->show();
?>

A Outputs: Child show

B Outputs: Base show

C Fatal error: Cannot override private method Base::show()

D Fatal error: Call to private method Base::show() from Child

💡 Hint

Private methods are not visible to child classes, so Child defines its own method.

The show method in Base is private, so Child does not override it but defines a new method. Calling $obj->show() calls Child's method, outputting "Child show".

📝 Syntax

advanced

Which option causes a syntax error in method overriding?

Which of the following PHP code snippets will cause a syntax error?

A

<?php
class A {
    public function test() {}
}
class B extends A {
    public function test() {
        parent::test();
        echo "Hi";
    }
}
?>

B

<?php
class A {
    public function test() {}
}
class B extends A {
    public function test() 
        echo "Hi";
    }
}
?>

C

<?php
class A {
    public function test() {}
}
class B extends A {
    public function test() {
        echo "Hello";
    }
}
?>

D

<?php
class A {
    public function test() {}
}
class B extends A {
    public function test() {
        return "Hi";
    }
}
?>

💡 Hint

Check for missing braces or incorrect function syntax.

Option B is missing the opening brace { after the method declaration, causing a syntax error.

🚀 Application

expert

Determine the final output with multiple overrides and parent calls

What is the output of this PHP code?

PHP

<?php
class A {
    public function message() {
        return "A";
    }
}

class B extends A {
    public function message() {
        return "B" . parent::message();
    }
}

class C extends B {
    public function message() {
        return "C" . parent::message();
    }
}

$obj = new C();
echo $obj->message();
?>

A CBA

B Error: Cannot call parent method

C CAB

D ABC

💡 Hint

Each class adds its letter and calls the parent's message method.

Class C calls B::message(), which calls A::message(). The output concatenates "C" + "B" + "A" = "CBA".