[UPHPU] strange mysqli error

[Richard K Miller]

I'm getting a weird mysqli error in my object destructor.  Here's an  
example:

<?php

$db = new mysqli('localhost', USERNAME, PASSWORD, DATABASE);

class Test
{
	function __construct()
	{
		global $db;
		
		$db->query("SELECT 'test'");
		print_r($db->error);
	}

	function __destruct()
	{
		global $db;
		
		$db->query("SELECT 'test'");  // line 20
		print_r($db->error);  // line 21
	}
}

$test = new Test();

?>


A. On my dev machine (Mac OS X + PHP 5.1.4 + MySQL 5.0.19) I get the  
following errors EVERY time:
Warning: mysqli::query() [function.mysqli-query]: Couldn't fetch  
mysqli in /Users/richard/Projects/data/private/mgftest.php on line 20
Warning: Test::__destruct() [function.Test---destruct]: Couldn't  
fetch mysqli in /Users/richard/Projects/data/private/mgftest.php on  
line 21

B. On my production server (FreeBSD + PHP 5.1.2 + MySQL 5.0.19) I  
SOMETIMES get the following error: (If I refresh the page repeatedly,  
sometimes there's an error, sometimes not.)
Warning: mysqli::query() [function.query]: Couldn't fetch mysqli in / 
usr/local/www/data/private/mgftest.php on line 20

C. On a Bluehost box (PHP 5.0.4 + MySQL 5.0.22) I NEVER get any errors.

There's nothing else in my error logs, $db-errno is 0, and $db->error  
is empty.  Interestingly, I never get any errors from the constructor.

Any ideas?

Richard