You receive an error message on your browser “Warning: Cannot modify header information – headers already sent by (output started at /path/blog/wp-config.php:34)” right after upgrading your WordPress or a new WordPress installation.
Solution: Remove Spaces, New Lines, Or Other Garbage In Wp-Config.Php
- Download wp-config.php via FTP.
- Open wp-config.php.
- Remove all spaces before <?php.
- Make sure the first characters are <?php, placed at the first line with no space in between.
- Remove all spaces after ?>
- Make sure the last characters are ?>, placed at the last line with no space in between.
This error could happen on other files too. Read the error message carefully as it states the specific file name where the error occurred.