<?php

interface Eatable {
   public function eat();
}

class A implements Eatable {
  public function eat() {return 1;}
}

function foo(Eatable $obj) {
  return $obj->eat();
}

foo(null);  // FAIL

?>

Catchable fatal error: Argument 1 passed to foo() must implement interface Eatable, null given, called in /t.php on line 15 and defined on line 11