This is Example Code of php Inheritance

<?php 

abstract class Shape {

	protected $color;

	public function __construct($color = 'blue')
	{
		$this->color = $color;
	}

	public function getColor()
	{
		return $this->color;
	}

	abstract protected function getArea();
	
}

class Square extends Shape {
	
	protected $length = 4;

	public function getArea()
	{
		return pow($this->length, 2);
	}
}

class Triangle extends Shape {

	protected $base = 4;

	protected $height = 7;

	public function getArea()
	{
		return .5 * $this->base * $this->height;
	}
}

class Circle extends Shape {

	protected $radius = 5;

	public function getArea()
	{
		return M_PI * pow($this->radius, 2);
	}
}

// long hand methods
// $circle = new Circle;

// echo $circle->getArea();

//shorthand
echo (new Circle)->getArea();