headers_sent Checks if or where headers have been sent boolheaders_sent string&file int&line headers_sent will return &false; if no HTTP headers have already been sent or &true; otherwise. 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. You can't add any more header lines using the header function once the header block has already been sent. Using this function you can at least prevent getting HTTP header related error messages. Another option is to use Output Buffering. The optional file and line parameters where added in PHP 4.3.0. link instead\n"; exit; } ?> ]]> See also ob_start, trigger_error, and header for a more detailed discussion of the matters involved.