What this usually means
The headers already sent warning usually means output was sent before WordPress or PHP tried to modify headers, cookies or redirects. The safest fix is to confirm the cause before changing files, plugins, server settings or database values on a live website.
Symptoms to look for
- Cannot modify header information
- Login cookies fail
- Redirects do not work
- Warning points to wp-config.php or functions.php
Developer-level causes
When this problem is more than a simple setting, a developer should check logs, file changes, plugin behavior, database state and hosting configuration before applying a fix.
- Whitespace before PHP opening tag
- UTF-8 BOM in edited file
- Echo/debug output in theme or plugin
- Syntax or include-order problem
Steps to check
- Read the first file path in the warning, not only the victim file.
- Check for whitespace or BOM in edited PHP files.
- Remove accidental output before redirects.
- Restore the file from a clean backup if needed.
- Retest login, redirects and affected pages.
When to ask for help
Ask for technical support if the website is down, revenue is affected, malware is suspected, wp-admin is blocked, checkout is failing, search traffic is at risk or the issue returns after a temporary fix. A specialist can review logs, isolate the cause and repair the site with less risk.
Related service
This guide connects to our PHP Error Fixing service for hands-on repair.
FAQ
Can I fix this WordPress problem myself?
You can run the basic checks if you have a verified backup and understand the risk. If the site is down, hacked, taking orders or showing PHP/database errors, developer support is safer.
What access is usually needed?
The safest repair usually needs WordPress admin access plus hosting, SFTP, database or log access depending on the error. If wp-admin is blocked, hosting access may be enough to start.
Which service fixes this issue?
This article is related to PHP Error Fixing, which covers diagnosis, repair, testing and a final report.