How to understand php datatype as object?

Question

PHP

I often see how a class or an interface is set as the type of arguments or return type. Something like this.
Or, I cut out two figures, in which the interface is declared as a type.

How to understand such a data type, what is obtained from the object as a value of the type, how can you be sure that what was intended will be pulled from the class? Well, I don't understand this at all. Tell me where to look, what to read.

Answer 1

If two classes implement the same interface, then you can use instanceof to understand which class came from and, depending on this, call the necessary actions.
https://www.php.net/manual/en/language.operators.t...