What is object-oriented programming (OOP) and how is it implemented in PHP? Provide examples of classes, objects, and inheritance.

Object-oriented programming (OOP) is a programming paradigm that organizes code around objects, which are instances of classes. It provides a way to structure code, promote reusability, and model real-world entities. In PHP, OOP is implemented through classes, objects, and inheritance. Here's an in-depth explanation along with examples:

1. Classes:

* A class is a blueprint or template for creating objects. It defines the properties (attributes) and behaviors (methods) that objects of that class will have.
* In PHP, you can define a class using the `class` keyword followed by the class name.
* Example:
```
php`class Car {
public $brand;
public $color;

public function startEngine() {
echo "Engine started!";
}
}`
```
* In the above example, the `Car` class has two properties: `$brand` and `$color`, and one method `startEngine()`.
2. Objects:

* An object is an instance of a class. It represents a specific entity or concept based on the class definition.
* To create an object in PHP, you use the `new` keyword followed by the class name and parentheses.
* Example:
```
php`$myCar = new Car();
$myCar->brand = "Toyota";
$myCar->color = "Blue";
$myCar->startEngine(); // Output: Engine started!`
```
* In the example, an object `$myCar` is created based on the `Car` class. The properties `$brand` and `$color` are assigned values, and the `startEngine()` method is called.
3. Inheritance:

* Inheritance is a fundamental concept in OOP that allows classes to inherit properties and behaviors from parent classes (superclasses).
* In PHP, you can define inheritance using the `extends` keyword.
* Example:


```
php`class ElectricCar extends Car {
public function chargeBattery() {
echo "Battery charged!";
}
}`
```
* In the above example, the `ElectricCar` class extends the `Car` class. It inherits the properties and methods of the `Car` class and defines an additional method `chargeBattery()`.
* Example (continued):


```
php`$myElectricCar = new ElectricCar();
$myElectricCar->brand = "Tesla";
$myElectricCar->color = "Red";
$myElectricCar->startEngine(); // Output: Engine started!
$myElectricCar->chargeBattery(); // Output: Battery charged!`
```
* In the example, an object `$myElectricCar` is created based on the `ElectricCar` class, which inherits the properties and methods from the `Car` class. Additional properties are assigned values, and both inherited and specific methods are called.

Object-oriented programming provides several benefits, such as code modularity, encapsulation, code reuse, and easier maintenance. By using classes, objects, and inheritance, PHP developers can build complex applications with organized and reusable code structures.