in php, a function's arguments can be a word without quotes or $

Question

I always thought that the arguments of a function in PHP should be either a string enclosed by '', or a number, or a variable.

However, looking at this in php.net's manual I see:

   public function baz(Test $other)

What does the word Test here refer to?

How is this possible?

Answer 1

PHP 5 supports "type hinting" for object or array parameters. If $other is not a Test object, there will be a runtime fatal error.

So make sure you catch the hint.

Answer 2

It means the argument to baz() should be of type Test.