Is this ZF2 constant var or datatype

Question

public function setAlbumTable(AlbumTable $albumTable)
{
$this->albumTable = $albumTable;
return $this;
}

I am talking about first parameter ( it's not parameter btw) looks like datatype ? what is it ? constant ? I encounter this when trying to develop app in zend framework 2

Answer 1

This is PHP's type hinting. It means that the first parameter to this function - $albumTable - must be an instance of the AlbumTable class or a class that inherits from it.

class Car {}

class BlueCar extends Car {}

function drive_the_car(Car $car) {}

drive_the_car(42); // error, first parameter must be an instance of Car

drive_the_car(new stdClass()); // error

drive_the_car(new Car()); // works

drive_the_car(new BlueCar()); // works

Answer 2

The piece of code you're showing is an example of dependency injection via setter method. The setter is passed an instance of AlbumTable and assignes this instance to a class field.

Your method is passed ONLY ONE parameter: $albumTable.

The AlbumTable before the parameter is a type hint and makes sure that only a instance of AlbumTable or a deriving class can be passed to the setter.

Answer 3

It forces the actual parameter ($albumTable) to be an instance of AlbumTable class. PHP will give a fatal error if anything else is passed to the function.

This is useful so you don't have to check what type of variable/object you received in order to make use of it's functions and properties.