Php logical expression and objects

Question

here is something weird to me.

Code 1:

if($city = Cities::find_by_id($city_id)) {
  var_dump($city);
}

This returns: object(Cities)#6 (7) {...}, ordinary

Code 2:

if($city = Cities::find_by_id($city_id) && $building = Buildings::find_by_id($building_id)) {
      var_dump($city);
}

This returns: bool(true), and I expect result like the one before

Can someone explain to me what is happening?

Answer 1

What is happening here is that in first case you are just assigning function return value to variable $city

$city = Cities::find_by_id($city_id)

and result is pretty much what you would expected. For the second case you are doing something different - you are assigning

Cities::find_by_id($city_id) && $building = Buildings::find_by_id($building_id)

to variable $city which means if Cities::find_by_id and Buildings::find_by_id both return stdObjects there is logical and operator applied.

It is something like:

$city = (object) && (object)

which is pretty much same as

$city = true && true

You would probably want to do something like that (see extra parentheses):

if(($city = Cities::find_by_id($city_id)) && ($building = Buildings::find_by_id($building_id))) {
  var_dump($city);
}