Inheritance in PHP (Extend Classes Correctly)

Inheritance allows a class to extend another class.

Example: base class + child class

<?php
class Employee {
  public function __construct(public string $name) {}

  public function role(): string {
    return "Employee";
  }
}

class Manager extends Employee {
  public function role(): string {
    return "Manager";
  }
}

$e = new Employee("David");
$m = new Manager("Sarah");

echo $e->role(); // Employee
echo $m->role(); // Manager
?>

When inheritance is useful

• you have a strong "is-a" relationship
  • Manager is an Employee

When to avoid

If you are just sharing code but relationship is not clear, composition (using another class inside) is often better.

Next: Interfaces, building flexible and testable code.