Hacking with HHVM

HACK
num += $delta;
return $this;
}
public function get(): int {
return $this->num;
}
public function __constructor(int $num): void {
$this->num = $num;
}
$f = new Foo(123);
$f->add(456);
$f->add(“banana”);
Basic Hack
▪ Static Analyzer traces value
through whole program
▪ Looks for mismatches and
reports errors
▪ “Foo::add() expected int”
“Foo::add() received string”