array keyword before function parameters in PHP

Question

I saw a function declared like this:

public static function factory($file=null, array $data=null, $auto_encode=null)

If you want to see the real class, please go to this view.php class from a fork of fuelphp parser package in github.

My question is, what does array keyword means in array $data = null?

Answer 1

This is an example of PHP5's type hinting. The parameter $data is supposed to be an array. It is possible to hint method parameters as either object or array types. If it is an object, you can specify the name of the class as the hint keyword.