class name in method along with variable

Question

I am reading about design patterns in PHP and I keep seeing the following syntax, for example

abstract class AbstractObserver { abstract function update(AbstractSubject $subject_in); }

or

class PatternObserver extends AbstractObserver { public function __construct() { } public function update(AbstractSubject $subject) { } }

(code is part of this example)

where "AbstractSubject" is another abstract class.

I am used to defining methods like methodName($var), not including a class name in there, like methodName(className $var).

So, what actually the class name does in a method ? My best guess is that it passes something like a reference in that class? Can you explain to me what it actually does?

Thanks

It's called Type Hinting, and it defines the datatype that the argument must be — Mark Baker
– Mark Baker, Commented Sep 18, 2017 at 21:32

genesst · Accepted Answer · 2017-09-18 21:35:00Z

1

It's called Type Hinting, since php 7 you can use scalar types to type hint parameters. (Some more)

answered Sep 18, 2017 at 21:35

genesst

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