PHP Header issue with ob_start() and ob_end_flush()

There's a lot of invisible output in your code:

 --- THERE IS A LINE RETURN HERE ---
--- SPACES OR TABS --- --- LINE RETURN ---
--- AND HERE ---     ...

Quit starting and ending your php tags. Just do this:

    ob_start();
    include_once("header.php");
    global $db;
    ...

Make absolutely sure that there is no output, and no whitespace outside of your tags before the call to ob_start(). If your error is on line 9, you've got a bunch of lines before that call that could be the problem. You may want to post all of those lines, numbered, so we can look at them carefully.