Readie - 12:24 pm on Aug 17, 2013 (gmt 0)
It's because you're mixing the mysqli object and the mysqli procedural functions together. You've also failed to asign anything to the variable $con that you are trying to use in your mysqli_query function.
If you replaced this line:
$mysqli = new mysqli($server, $user, $pass, $db);
$con = mysqli_connect($server, $user, $pass, $db);
Then it looks like it should work.