I'm trying to use SSI in a node and I'm getting all kinds of errors.
I'm able to include text files such as file.txt, file.html.

But when I
virtual ( 'sites/default/mystuff/file.cgi' )
or
virtual ( 'sites/default/mystuff/file.php' )
or
virtual ( 'sites/default/mystuff/file.shtml' )

I get errors like these:
Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/www_root/modules/php/php.module(80) : eval()'d code:3) in drupal_send_headers() (line 1243 of /var/www/html/www_root/includes/bootstrap.inc).
Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/www_root/modules/php/php.module(80) : eval()'d code:3) in drupal_send_headers() (line 1243 of /var/www/html/www_root/includes/bootstrap.inc).
Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/www_root/modules/php/php.module(80) : eval()'d code:3) in drupal_send_headers() (line 1243 of /var/www/html/www_root/includes/bootstrap.inc).
Notice: ob_end_clean(): failed to delete buffer. No buffer to delete. in php_eval() (line 82 of /var/www/html/www_root/modules/php/php.module).
Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/www_root/modules/php/php.module(80) : eval()'d code:3) in drupal_send_headers() (line 1243 of /var/www/html/www_root/includes/bootstrap.inc).
Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/www_root/modules/php/php.module(80) : eval()'d code:3) in drupal_send_headers() (line 1243 of /var/www/html/www_root/includes/bootstrap.inc).