Using is_a or instanceof 1. is_a being a function takes an object as parameter 1, and a string (variable, constant, or literal) as parameter 2. So; ```is_a($object, $string); //only way to call it``` 2. instanceof takes an object as parameter 1, and can take a class name (variable), object instance (variable), or class identifier (class name wri…

AreaCalculator.php

<?php

class AreaCalculator {

public function calculate($shapes)
  {
    //using is_a
    
    if(is_a($shape, 'Square') //
    {
      //bla bla bla
    }
    
    //using instanceof
    
    if($shape instanceof Square) //Square is another class
    {
      //bla bla bla
    }
  
  }
}