continua a dare questi errori

Warning: fopen(config.txt) [function.fopen]: failed to open stream: Permission denied in C:\Programmi\Apache Group\Apache2\htdocs\test\scrivi.php on line 16

Warning: fwrite(): supplied argument is not a valid stream resource in C:\Programmi\Apache Group\Apache2\htdocs\test\scrivi.php on line 19

Warning: fclose(): supplied argument is not a valid stream resource in C:\Programmi\Apache Group\Apache2\htdocs\test\scrivi.php on line 20