php - What does "return $this" mean? -

i'm trying understand code, , when arrived @ final line, didn't it. :(

can have in order find out, return $this mean ?

public function setoptions(array $options) {     $methods = get_class_methods($this);     foreach ($options $key => $value) {         $method = 'set' . ucfirst($key);         if (in_array($method, $methods)) {             $this->$method($value);         }     }      //???? - return ?     return $this; } 

update:
i've removed comments better clarification.

this way of coding called fluent interface. return $this returns current object, can write code this:

$object   ->function1()   ->function2()   ->function3()   ; 

instead of:

$object->function1(); $object->function2(); $object->function3();