http://blog.loftdigital.com/its-dangerous-to-go-alone

takeThis.php

class SimpleCounter {
     
     protected $total = 0;
     
     public function add($amount) 
         $this->total += $amount
         return $this
     }
       
     public function subtract($amount) 
         $this->total -= $amount
         return $this
     }
       
     public function getTotal() 
         return $this->total;
     }
 }
And now...

$counter = new SimpleCounter();
 echo $counter->add(5)
     ->subtract(3)
     ->add(2)
     ->getTotal();
 // 4
 echo $counter->getTotal();
 // 4