The PHP header() function is not redirecting [closed]

Question

I am using the following PHP code to check a session. But if the session is not logged into then the page is not redirected and just shows the black page.

My if condition is right! It is hitting the header function...

Here is my code:

if(
    !isset($_SESSION['SESS_MEMBER_ID'])
    || (trim($_SESSION['SESS_MEMBER_ID']) == '')
    AND !isset($fb_login)
) {
    header("location:login.php?msg=Please+Login+Again.");
}

How can I fix it?

HTTP/1.1 200 OK
Date: Wed, 10 Oct 2012 10:57:14 GMT
Server: Apache/2.2.15 (CentOS)
X-Powered-By: PHP/5.3.3
Connection: close
Transfer-Encoding: chunked
Content-Type: text/html; charset=UTF-8

Answer 1

If you're using header("Location: "); after you've output content make sure you've put ob_start(); earlier in the script. ob_start(); buffers your script, so nothing is output until you either call ob_end(); or the end of the file is reached. Calling header("Location: "); after content has already been output to the browser can cause problems.