Cannot modify header information

Overview

This article offers different options to resolve the common "Cannot modify header information" PHP error.

Background

You may notice the following error either on your PHP website:

This is essentially an issue with how the site is coded. It states that something was sent to the browser before the PHP header() function was called, and once the header block has already been sent, you cannot add additional header lines.

How to fix this error

There are two ways you can resolve this error.

Using a phprc file (easy)

You can create/edit your user's phprc file and add a few lines to resolve this. See the following articles for instructions on how to create a phprc file:

• Create a phprc file via FTP
• Create a phprc file via SSH

If the file already exists, view the following articles for instructions on how to update it (depending on if you're using an FTP client or SSH):

• Creating and editing a file via FTP
• Creating and editing a file via SSH

Once created, add the following lines to the phprc file:

output_buffering = 4096

Editing the PHP code (advanced)

This error is most often caused by your code sending output to the browser before the header() function. To resolve this, you (or a developer) would need to manually edit the website's code so the header() function is set before any output.

See also

• php.ini overview
• Create a phprc file via FTP
• Create a phprc file via SSH
• My phprc file isn't updating