If you receive a warning on your pages similar to the one below:
"Warning: Cannot modify header information - headers already sent by (output started at /home/user/public_html/index.php:581) in /home/user/public_html/system/sessions.php on line 180"
there are a few things you can do in order to fix the issue:
1. You should check for any empty lines at the end of your .php files. This is a common issue with some web applications. Simply remove the empty line at the end of your script( after the final "?>" or "php>" string) and check your website again.
2. You can make a local php.ini & .user.ini file in the folder of your script and add the following line in it:
buffer_output = on
3. If the warnings are not affecting the functionality of your website, you can simply hide them.