PHP Switch语句：这是正确的吗？

Question

I've taken a look at the documentation for switch on php.net and as best as I can tell it checks a equality comparison between the variable in the switch and the case. However, the following code seems to work properly for all possible values (int, null, array, other):

$x = array('one','two');

switch ($x) {
   case null:
      echo "is null!";
      break;
   case is_int($x):
       echo "is int";
       break;
   case is_array($x):
      echo "is array!";
      break;
   default:
      echo "something else!";
      break;
}

From what I read, it should be comparing is_int($a) [true] to $x [an array, which evaluates to true] and giving an incorrect result.

My question is ... why is this actually working?

EDIT: sorry I had not copied it quite correctly as I'd been messing about with it. Its now in its working form

Answer 1

is_int($x) does not evaluate to true if x is an array. This works because array('one', 'two') is considered true, and is_array() will evaluate to true. This means it does not match null or is_int($x) (the latter comes out to false). If it's an int, then the opposite is true and is_array($x) becomes false. If $x is null, it evaluates to false, as does null in the switch. The null case will be executed for any circumstance where $x is false (try it with false, array(), 0, and others).