headers_sent
bool headers_sent([string &file [, int &line]] )
using headers_sent function we can check whether the HTTP headers have already been sent or not. IF its sent then it will return TRUE and FALSE on no header sent.
If the optional file and line parameters are set, headers_sent() will put the PHP source file name and line number where output started in the file and line variables.
With this function we can at least prevent getting HTTP header related error messages.
