Question about var_dump output

When I var_dump an开发者_开发技巧 object, the output looks like this:

object(XCTemplate)#2477 (4) {
  ["id"]=>
  string(1) "1"
  ["attributes"]=>
  array(0) {
  }
  ["db_table_name"]=>
  string(14) "template_names"
  ["cache"]=>
  array(0) {
  }
}

XCTemplate is its class, of course, but what does the integer (here: 2477) after the # mean?

It's a unique id associated with that particular instance of XCTemplate. AFAIK this is not documented, and also there is no way to get it (other than using var_dump()); and I've looked at the Reflection class.

From what I've seen:

• The ids are unique to every instantiation; starting at 1 and incrementing by 1 with every new object. This includes every object; they don't have to be of the same class.
• Destroying an instance (eg: through unset) frees up its id and the next instantiated object can (and will) use it.

• It's not related to the variable; eg:

  $foo = new Foo();
  var_dump($foo);
  $foo = new Foo();
  var_dump($foo);
  

  Will produce different id's for different instantiations.

• This is not the same as resource ids, where you can just convert to int to get the id:

  $resource= curl_init();      
  var_dump($resource);       // resource #1 of type curl
  print(intval($resource));  // 1
  print((int) $resource);    // 1