In some cases we find the following error from Apache logs:
[wpfmb type=’error’ theme=2]PHP Warning: Cannot modify header information – headers already sent by [/wpfmb]
We can fix this error by updating a php.ini file.
Find the domain’s php.ini file. If there is no php.ini file, you have to create one.
Open the file and locate the line:
output_buffering = Off
Change the line as follows:
output_buffering = On
Also, increase “maximum_execution_time” to 300.
Save the php.ini file and restart Apache service.
After making this change, issue will be fixed and your website will be back online.