Method overriding in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is method overriding in PHP?

Method overriding in PHP is when a child class defines a method with the same name as a method in its parent class, replacing the parent's method behavior.

beginner

Why do we use method overriding?

We use method overriding to change or extend the behavior of a method inherited from a parent class, allowing child classes to customize functionality.

intermediate

How do you call the parent class method inside an overridden method in PHP?

You use <code>parent::methodName()</code> inside the child class method to call the parent class's version of the method.

beginner

What happens if the child class does not override a method from the parent class?

If the child class does not override the method, it inherits and uses the parent's method as is.

intermediate

Can private methods be overridden in PHP?

No, private methods cannot be overridden because they are not accessible to child classes.

What keyword is used to call the parent class method inside an overridden method in PHP?

A parent::

B super::

C this::

D base::

In PHP, parent::methodName() calls the parent class's method.

If a child class overrides a method, which method is executed when called on the child object?

A Child class method

B Parent class method

C Both methods

D None

The child class method overrides the parent method and is executed.

Can a private method in a parent class be overridden by a child class in PHP?

A Yes, always

B Only if declared final

C No, private methods are not accessible

D Only if static

Private methods are not visible to child classes, so they cannot be overridden.

What happens if a child class does not override a method from its parent?

A Error occurs

B Parent method is used

C Method is ignored

D Child class must define it

The child class inherits and uses the parent's method if it does not override it.

Which of these is a reason to override a method?

A To avoid inheritance

B To delete the parent method

C To make the method private

D To change inherited method behavior

Overriding lets you change or extend the behavior of an inherited method.

Explain method overriding in PHP and how it helps in object-oriented programming.

Think about how child classes can change what they inherit.

Describe how to call a parent class method from an overridden method in PHP and why you might want to do that.

Sometimes you want to add to the parent's method, not just replace it.

Practice

1. What does method overriding allow a child class to do in PHP?

easy

A. Change the behavior of a method inherited from the parent class

B. Create a new method with a different name

C. Prevent the parent class from being instantiated

D. Automatically call all parent methods

Solution

1. Step 1: Understand method overriding concept

   Method overriding means a child class uses the same method name as the parent to change its behavior.

2. Step 2: Identify what overriding does

   It replaces or modifies the parent's method behavior in the child class.

3. Final Answer:

   Change the behavior of a method inherited from the parent class -> Option A

4. Quick Check:

   Method overriding = change parent method behavior [OK]

Hint: Overriding means same method name, new behavior [OK]

Common Mistakes:

• Thinking overriding creates new methods with different names
• Confusing overriding with inheritance itself
• Believing overriding prevents parent instantiation

2. Which of the following is the correct syntax to override a method named greet in a child class in PHP?

easy

A. function greetChild() { /* new code */ }

B. function greet() { /* new code */ }

C. override function greet() { /* new code */ }

D. parent::greet() { /* new code */ }

Solution

1. Step 1: Recall method overriding syntax

   To override, define a method with the same name in the child class.

2. Step 2: Check options for correct syntax

   Only function greet() { /* new code */ } defines function greet() correctly without extra keywords.

3. Final Answer:

   function greet() { /* new code */ } -> Option B

4. Quick Check:

   Same method name in child = override [OK]

Hint: Use same method name in child class to override [OK]

Common Mistakes:

• Adding 'override' keyword which PHP does not use
• Changing method name to something else
• Trying to call parent method syntax incorrectly

3. What will be the output of this PHP code?

class ParentClass {
  function sayHello() {
    echo "Hello from Parent";
  }
}
class ChildClass extends ParentClass {
  function sayHello() {
    echo "Hello from Child";
  }
}
$obj = new ChildClass();
$obj->sayHello();

medium

A. Hello from ParentChild

B. Hello from Parent

C. Hello from Child

D. Error: Method not found

Solution

1. Step 1: Identify method overriding in ChildClass

   ChildClass defines sayHello() which overrides ParentClass method.

2. Step 2: Check which method is called

   Creating ChildClass object calls ChildClass's sayHello(), printing "Hello from Child".

3. Final Answer:

   Hello from Child -> Option C

4. Quick Check:

   Child method overrides parent = "Hello from Child" [OK]

Hint: Child method runs if overridden, not parent [OK]

Common Mistakes:

• Expecting parent method output instead of child
• Thinking both outputs print together
• Assuming error due to method name clash

4. Find the error in this PHP code that tries to override a method:

class Base {
  function show() {
    echo "Base";
  }
}
class Derived extends Base {
  function show() {
    parent.show();
    echo " Derived";
  }
}
$obj = new Derived();
$obj->show();

medium

A. Class Derived must declare show() as public

B. Cannot override methods in PHP

C. Missing return statement in show()

D. Incorrect syntax to call parent method; should use parent::show()

Solution

1. Step 1: Identify how parent method is called

   The code uses parent.show() which is invalid syntax in PHP.

2. Step 2: Correct syntax for calling parent method

   PHP requires parent::show() to call the parent's method inside child.

3. Final Answer:

   Incorrect syntax to call parent method; should use parent::show() -> Option D

4. Quick Check:

   Call parent method with parent::method() [OK]

Hint: Use parent::method() to call parent method inside child [OK]

Common Mistakes:

• Using dot (.) instead of :: to call parent method
• Thinking overriding is not allowed
• Forgetting to call parent method when needed

5. Given these classes, what will be the output?

class Animal {
  function sound() {
    echo "Some sound";
  }
}
class Dog extends Animal {
  function sound() {
    parent::sound();
    echo " and Bark";
  }
}
class Puppy extends Dog {
  function sound() {
    echo "Yip";
  }
}
$pet = new Puppy();
$pet->sound();

hard

A. Yip

B. Some sound and Bark and Yip

C. Some sound and Bark

D. Error: Cannot override multiple times

Solution

1. Step 1: Trace method calls for Puppy object

   Puppy overrides sound() and only echoes "Yip" without calling parent.

2. Step 2: Understand overriding chain

   Since Puppy method does not call parent::sound(), Dog and Animal methods are not executed.

3. Final Answer:

   Yip -> Option A

4. Quick Check:

   Child override without parent call = only child output [OK]

Hint: If child method skips parent call, only child output shows [OK]

Common Mistakes:

• Assuming all parent methods run automatically
• Expecting combined outputs without explicit parent calls
• Thinking multiple overrides cause errors