Fix the “Cannot Modify Header Information – Headers Already Sent By” Error

 

The “Cannot Modify Header Information – Headers Already Sent By” error occurs when there is whitespace or other output before the HTTP headers are sent. This can happen for a few reasons, such as:

1. Extra spaces or new lines before the opening PHP tag in a PHP file.
2. BOM (Byte Order Mark) characters at the beginning of the file.
3. An extra echo or print statement before the header() function is called.
4. A plugin or theme that is improperly coded and sends output before the headers are sent.

To fix this error, you can try the following steps:

1. Check for extra spaces or new lines before opening the PHP tag in the file causing the error. Remove any extra spaces or new lines and save the file.
2. Check for BOM characters at the beginning of the file. BOMs are invisible characters that can cause this error. You can remove them with a text editor that has BOM support.
3. Check for extra echo or print statements before the header() function is called. Remove any extra output and save the file.
4. If a plugin or theme causes the error, try disabling or removing the plugin or theme to see if it resolves the issue.
5. If a plugin causes the issue, you can try re-installing the plugin or contact the plugin developer for assistance.
6. Check your server error logs; this can give you more information about where the problem is coming from.
7. If none of the above steps works, you may need to consult with a developer to help you troubleshoot the issue further.

It’s worth mentioning that the error message is not always pointing to the exact location of the problem, so you might need to check multiple files, especially if you are working on a big project.