Testing...
<?php
if (!extension_loaded('mysqli')) die('oops, mysqli not supported');
error_reporting(E_ALL | E_STRICT);


// mysqli Connect-Time Error-Condition Bugs
// ----------------------------------------
// Testing all 9 combinations of (bogus host, bogus login, AOK) 
// versus (object oriented, procedural, classic mysql).
// Each (non-classic) test case ends checking the "drastic workaround" for the 4 bugs.
// The "drastic workaround" may break depending on how bugs 3,4 were fixed.



// Bogus Host - object oriented

$mysqli = @new mysqli('bogushost.com');
assert( 0===mysqli_connect_errno());          // BUG #1: a host error is not a connect_error (serious)
assert(''===mysqli_connect_error()); 
assert(FALSE != $mysqli);                     // BUG #2: constructor never FALSE (minor)
assert('object'==gettype($mysqli));
assert('mysqli'==get_class($mysqli));
assert($mysqli instanceof mysqli);
assert(@is_a($mysqli, 'mysqli'));             // (suppress the "strict" warning: is_a() deprecated)
assert(!isset($mysqli->error));               // BUG #3: isset *never* true (see AOK case below)
// any other $mysqli access generates warning // BUG #4: instance limbo (minor)
assert(NULL===@$mysqli->error);               // drastic workaround, @ supresses the warning



// Bogus Host - procedural

$mysqli = @mysqli_connect('bogushost.com');
assert( 0==mysqli_connect_errno());           // BUG #1
assert(''==mysqli_connect_error());
assert(FALSE===$mysqli);                      // gentle workaround (but not for object oriented)
assert(NULL===@mysqli_error($mysqli));



// Bogus User/Password - object oriented

$mysqli = @new mysqli('visibone.com', 'bogususer', 'boguspassword');
assert( 0 != mysqli_connect_errno());        // gentle workaround (but not for host error)
assert(1045==mysqli_connect_errno());
assert('' != mysqli_connect_error()); 
assert(preg_match('/Access denied/', mysqli_connect_error()));
assert(FALSE != $mysqli);                     // BUG #2
assert('object'==gettype($mysqli));
assert('mysqli'==get_class($mysqli));
assert(!isset($mysqli->error));
assert(NULL===@$mysqli->error);



// Bogus User/Password - procedural

$mysqli = @mysqli_connect('visibone.com', 'bogususer', 'boguspassword');
assert(1045===mysqli_connect_errno());
assert(preg_match('/Access denied/', mysqli_connect_error()));
assert(FALSE===$mysqli);
assert(NULL===@mysqli_error($mysqli));



// To see the non-error conditions, fill in the *** blanks.

$HOST = '***';
$USER = '***';
$PASS = '***';
$DATABASE = '***';
@include('secure/passwords.php');



// AOK Connection - object oriented

$mysqli = new mysqli($HOST, $USER, $PASS, $DATABASE);
assert( 0===mysqli_connect_errno()); 
assert(''===mysqli_connect_error()); 
assert('object'==gettype($mysqli));
assert('mysqli'==get_class($mysqli));
assert(!isset($mysqli->error));               // BUG #3: $mysqli->error is a ghost property (minor)
assert(!property_exists($mysqli, 'error'));
assert(!property_exists('mysqli', 'error'));  // So how can you detect a failed connect?
assert(''===$mysqli->error);   
assert(NULL!==@$mysqli->error);               // This is the only way I found.

$result = $mysqli->query("SHOW TABLES");      // a good query
assert($result != FALSE);
assert('mysqli_result'==get_class($result));
assert(''===$mysqli->error);
assert( 0===$mysqli->errno);
assert(!isset($mysqli->error));               // BUG #3 even after a good query
assert(!property_exists($mysqli, 'error'));
assert(!property_exists('mysqli', 'error'));
assert('integer'==gettype($result->num_rows));
assert($result->num_rows > 0);
echo "$result->num_rows tables\n";
assert(!isset($result->num_rows));            // BUG #3: num_rows also a ghost property (maybe they all are?)
assert(!property_exists($result, 'num_rows'));
assert(!property_exists('mysqli_result', 'num_rows'));
$result->close();

$result = $mysqli->query("SNOW FABLES");      // a bogus query
assert($result === FALSE);
assert('' != $mysqli->error);
assert( 0 != $mysqli->errno);
assert(1064 == $mysqli->errno);
assert(!isset($mysqli->error));               // BUG #3 even after a BAD query
assert(!isset($mysqli->errno));
assert(!property_exists($mysqli, 'error'));
assert(!property_exists('mysqli', 'error'));


$mysqli->close();



// AOK Connection - procedural

$mysqli = mysqli_connect($HOST, $USER, $PASS, $DATABASE);
assert( 0===mysqli_connect_errno()); 
assert(''===mysqli_connect_error()); 
assert('object'==gettype($mysqli));
assert('mysqli'==get_class($mysqli));
assert(''===mysqli_error($mysqli));
assert(NULL!==@$mysqli->error);

mysqli_close($mysqli);



///////////////////// a review of the classic mysql functions /////////////////////////////



// Bogus Host - classic mysql

$mysql = @mysql_connect('bogushost.com');
assert(FALSE===$mysql);     
assert('' != mysql_error());              // no bug 1 in classic mysql
assert( 0 != mysql_errno());
assert(preg_match('/Unknown MySQL server host/', mysql_error()));
assert(2005 == mysql_errno());



// Bogus User/Password - classic mysql

$mysql = @mysql_connect('visibone.com', 'bogususer', 'boguspassword');
assert(FALSE===$mysql);
assert('' != mysql_error());
assert( 0 != mysql_errno());
assert(preg_match('/Access denied/', mysql_error()));
assert(1045 == mysql_errno());



// AOK - classic mysql

$mysql = mysql_connect($HOST, $USER, $PASS, $DATABASE);
assert(FALSE!==$mysql);
assert('' === mysql_error());
assert( 0 == mysql_errno());
mysql_close($mysql);



?>
...Done.