Cannot modify header information, headers already sent [duplicate]

Answer 1

To ensure your error reporting level is the same across environments, you can set it in your application using error_reporting() and ini_set('display_errors', 1)

Also check your .php files for any whitespace before the opening tag and after the closing tag.

In addition to the points mentioned above, ensure you are not outputting anything before the headers are set, for example the following code would produce an error similar to the one you are receiving:

echo 'Hello, World';
header('Location: http://www.somesite.com');