1. Check for White Space: The most common cause of the “Cannot Modify Header Information” error is extra white space at the beginning or end of your PHP files. Check all of your theme and plugin files for extra white space before and after the opening and closing PHP tags.
2. Check for Output Buffering: Output buffering can also cause the “Cannot Modify Header Information” error. Check your theme and plugin files for any calls to ob_start(), ob_get_contents(), and ob_end_clean().
3. Check for PHP Redirects: PHP redirects can also cause the “Cannot Modify Header Information” error. Check your theme and plugin files for any calls to header() or wp_redirect().
4. Check for WordPress Functions: WordPress functions such as wp_head() and wp_footer() can also cause the “Cannot Modify Header Information” error. Check your theme and plugin files for any calls to these functions.
5. Check for PHP Sessions: PHP sessions can also cause the “Cannot Modify Header Information” error. Check your theme and plugin files for any calls to session_start().
6. Check for Other PHP Errors: If none of the above solutions work, then you may have a more serious PHP error. Check your error logs for any other PHP errors that may be causing the “Cannot Modify Header Information” error.
If you encountered WordPress “Cannot modify header information” error, that means there’s something wrong with your website’s page header code. Not to worry — we’re here to help! In this article, we will discuss why this error occurs in the first place and how to fix the issue in no time.
In WordPress CMS, this error occurs when there’s a faulty code in your page header. For example, the message will look similar to this:
Warning: Cannot modify header information – headers already sent by (output started at /public_html/wp-content/plugins/my-plugin/my-function.php:#) in /public_html/wp-includes/pluggable.php on line #
Two files are usually mentioned and the source of the problem originates from the first one which prevents the other from functioning properly. Meanwhile, line # indicates the location of the faulty code, which helps you locate the issue without having to scour the file manually.
In most cases, having extra blank spaces (whitespaces) or sending the output before calling the header first causes the error. With the help of the information in the error message, you should be able to solve this issue in no time.
Typos, incorrect software configuration, and header misplacement are some of the most common causes of this error.
Here’s how to troubleshoot WordPress “Cannot modify header information” message:
1. Editing Corrupted Files
If the faulty file has whitespaces, the easiest way to solve the issue is to manually edit the issue via an FTP client like FileZilla or a File Manager. You can start from line # mentioned in the error message, then look through the rest of the file for any unnecessary spaces.
Make sure to pay attention to the beginning and end of PHP tags. There should be no spaces before the <?php tag or after the closing ?> tag and file’s last line of the code.
Most text editors can remove whitespaces automatically. Alternatively, you can use online whitespace removal tools like TextFixer and Code Beautify to do the job for you.
2. Replacing Corrupted Files
If the “Cannot modify header information” error originates from a plugin or theme, you can easily solve it by re-installing the software. If it’s a WordPress core file, your best solution is to replace the faulty file with a clean version and reboot the website. The new installation will generate the proper file automatically.
By default, the header must be called first before sending any output from the body. Sending output before calling the header, including having unparsed HTML sections in the PHP file, likely causes the error. Here’s what an incorrect code will look like:
<html> <?php header('Location: http://www.hostinger.com/'); ?>
To solve this issue, you need to find the statements that send output above the header. Then, move the header statement on top of the faulty statement and make any necessary modifications to the code accordingly.
Whether you pasted a code snippet to your file, installed a new plugin or theme, or write the code manually, you risking adding extra blank spaces to the file. If you’re not careful, these might trigger the “Cannot modify header information” error.
Did you find our tutorial helpful in solving this WordPress error? Let us know in the comments section below!
How to Fix WordPress “Cannot Modify Header Information” Message
If you’re a WordPress user, you may have encountered the “Cannot Modify Header Information” error message. This error can be caused by a variety of issues, including incorrect file permissions, improperly configured plugins, or even a corrupted .htaccess file. Fortunately, there are a few simple steps you can take to fix this issue.
Step 1: Check File Permissions
The first step in troubleshooting the “Cannot Modify Header Information” error is to check the file permissions of your WordPress files. WordPress requires certain files and folders to have specific permissions in order to function properly. To check the permissions of your WordPress files, you can use an FTP client such as FileZilla.
Once you’ve connected to your server via FTP, navigate to the root directory of your WordPress installation. From there, you can check the permissions of each file and folder. WordPress requires the following permissions:
- Directories: 755
- Files: 644
If any of your files or folders have incorrect permissions, you can change them using your FTP client. Once you’ve changed the permissions, try accessing your WordPress site again to see if the error has been resolved.
Step 2: Deactivate Plugins
If the file permissions are correct, the next step is to deactivate any plugins that may be causing the issue. To do this, log into your WordPress dashboard and navigate to the Plugins page. From there, you can deactivate each plugin one by one. After deactivating each plugin, try accessing your WordPress site again to see if the error has been resolved.
Step 3: Check .htaccess File
If deactivating plugins doesn’t resolve the issue, the next step is to check your .htaccess file. The .htaccess file is a configuration file that controls how your server handles certain requests. If the file is corrupted or contains incorrect information, it can cause the “Cannot Modify Header Information” error.
To check your .htaccess file, you can use an FTP client such as FileZilla. Once you’ve connected to your server via FTP, navigate to the root directory of your WordPress installation. From there, you should be able to locate the .htaccess file. If the file is present, you can download it to your computer and open it in a text editor.
If the file is corrupted or contains incorrect information, you can delete it and then create a new .htaccess file. To do this, you can use the WordPress Codex as a guide. Once you’ve created the new .htaccess file, upload it to your server and try accessing your WordPress site again to see if the error has been resolved.
The “Cannot Modify Header Information” error can be a frustrating issue to troubleshoot, but it can usually be resolved by checking the file permissions, deactivating plugins, or checking the .htaccess file. If you follow the steps outlined in this article, you should be able to resolve the issue quickly and get your WordPress site back up and running.