PHP类方法参数声明

class myClass {
   function myFunct(Foo $var) {
      ...
   }

   function otherFunct(myClass $other) {
        ...
   }
}

I've seen this declaration couple times in php manual however i dont get it, in this particular example what purpose it serving to have Foo and/or myClass in arguments list for a function?

Is there any use for this declaration outside of class?

Never mind i found it called type declaration (type hints) http://php.net/manual/en/functions.arguments.php#functions.arguments.type-declaration