1) Find the header() statement that is causing the problem. The error must be at or before this line.
2) Look for any statements that could send output to the user before this header statement. If you find one or more, find some way to move the header statement before them. Complex conditional statements may complicate the issue, but they may also help solve the problem. Consider a conditional expression at the top of the PHP script that determines the header value as early as possible and sets it there.
3) Make sure there is no white space outside of the php start and end tags. While a blank line before the <?php start tag may look innocent, when processed by PHP, it will turn into an echo statement printing out a blank line. This is a common culprit.
4) Add these two lines in configuration.php
$mosConfig_locale_debug = 0; $mosConfig_locale_use_gettext = 0;
Version: PHP version 5.2.9