Php type hinting to object properties existance -

how can hint, argument receive must have several public properties?
like:

interface iperson {     public $surname;     public $name; } class {     public function foo(iperson $p) {         return $p->surname . ' ' . $p->name;     } } 

but since interfaces can't point variables (why?), behavior above possible in php?
may there in new php releases(5.5-7.0)?

i think main issue php type system, no has property concept?

define getters in interface:

interface iperson {     public function getsurname();     public function getname(); } class {     public function foo(iperson $p) {         return $p->getsurname() . ' ' . $p->getname();     } }