Cannot modify header information, headers already sent by, ,
Why does it happen?
To understand why headers must be sent before output it’s necessary to look at a typical HTTPresponse. PHP scripts mainly generate HTML content, but also pass a set of HTTP/CGI headers to the webserver:
Without a sample of the actual code where this error is occurring, it’s impossible to pinpoint the exact issue.
Generally-speaking though, this means that you are outputting something before the header declaration. A good example of this is a PHP script that has code for setting a cookie after the same script has already used echo to output information.