Type hinting with Interfaces PHP - Example 2

Type hinting with Interfaces PHP 2 .php

<?php 

// output : 
// 53.454492$
// 55.977413122858$  

interface  CarInterface {
  public function calcTankVolume();
}

class Bmw implements CarInterface {
 protected $model;
  protected $height;
  
  protected $rib;
  
  public function __construct($model, $rib, $height)
  {
    $this -> model = $model;
    $this -> rib = $rib;
    $this -> height = $height;
  }
   
  // Calculates a rectangular tank volume
  public function calcTankVolume()
  {
    return $this -> rib * $this -> rib * $this -> height;
  } 
}
 
 
class Mercedes implements CarInterface {
  protected $radius;
  protected $model;
  protected $height;
   
  public function __construct($model, $radius, $height)
  {
    $this ->model = $model;
    $this -> radius = $radius;
    $this -> height = $height;
  }
 
  
  // Calculates the volume of cylinders
  public function calcTankVolume()
  {
    return $this -> radius * $this -> radius * pi() * $this -> height;
  }
}


// Type hinting ensures that the function gets only objects 
// that belong to the Car interface
function calcTankPrice(CarInterface $car, $pricePerGalon)
{
  echo $car -> calcTankVolume() * 0.0043290 * $pricePerGalon . "$";
}

$bmw1 = new Bmw('62182791', 14, 21); 
echo calcTankPrice($bmw1, 3);

echo PHP_EOL; 

$mercedes1 = new Mercedes('12189796', 7, 28); 
echo calcTankPrice($mercedes1, 3);

?>