Method overriding in PHP - Step-by-Step Execution

Concept Flow - Method overriding

Define Parent Class with Method

↓

Define Child Class with Same Method

↓

Create Child Object

↓

Call Method on Child Object

↓

Child's Method Runs, Overrides Parent's

↓

Output Result

The child class defines a method with the same name as the parent class, so when called on the child object, the child's method runs instead of the parent's.

Execution Sample

PHP

<?php
class ParentClass {
  function greet() {
    echo "Hello from Parent\n";
  }
}
class ChildClass extends ParentClass {
  function greet() {
    echo "Hello from Child\n";
  }
}
$obj = new ChildClass();
$obj->greet();
?>

This code shows a parent and child class both with a greet method; calling greet on the child object runs the child's version.

Execution Table

Step	Action	Class	Method Called	Output
1	Define ParentClass with greet()	ParentClass	N/A	N/A
2	Define ChildClass extending ParentClass with greet()	ChildClass	N/A	N/A
3	Create object of ChildClass	ChildClass	N/A	N/A
4	Call greet() on ChildClass object	ChildClass	greet()	Hello from Child
5	End of script	N/A	N/A	N/A

💡 Script ends after calling greet() on ChildClass object which overrides ParentClass method

Variable Tracker

Variable	Start	After Step 3	Final
$obj	undefined	ChildClass object	ChildClass object

Key Moments - 2 Insights

Why does calling greet() on the child object run the child's method, not the parent's?

Because in step 4 of the execution_table, the method called is greet() from ChildClass, which overrides the parent's greet() method.

What happens if the child class does not define greet()?

Then calling greet() on the child object would run the parent's greet() method, since the child inherits it without overriding.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output when greet() is called on the child object?

A No output

B Hello from Parent

C Hello from Child

D Error

💡 Hint

Check step 4 in the execution_table where greet() is called on ChildClass object.

At which step is the child class's greet() method defined?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the action column in the execution_table for method definitions.

If the child class did not override greet(), what would be the output at step 4?

A Hello from Parent

B Hello from Child

C No output

D Error

💡 Hint

Think about inheritance and method overriding explained in key_moments.

Concept Snapshot

Method overriding in PHP:
- Child class defines a method with the same name as parent.
- Child's method replaces parent's when called on child object.
- Use extends keyword for inheritance.
- Calling method on child object runs child's version.
- If child doesn't override, parent's method runs.

Full Transcript

This example shows method overriding in PHP. First, a parent class defines a greet method. Then a child class extends the parent and defines its own greet method with the same name. When we create an object of the child class and call greet, the child's greet method runs, printing 'Hello from Child'. This happens because the child's method overrides the parent's. If the child did not define greet, calling greet on the child object would run the parent's method instead. This is how method overriding lets child classes change or extend behavior of parent classes.