I have two files, one php file and one log file. The permission has been changed to the following:

-rwxr-x--- 1 www-data www-data 294 2012-06-25 10:17 function.php

-rwxr-x--- 1 www-data www-data 0 2012-06-25 09:53 log.txt

The permission is set to 750.

when I call function.php, I receive the following error message

fopen(log.txt): failed to open stream: Permission denied

This is the line :

$fp = fopen("log.txt","a");

I am very confused. I have php and the file to be written both under www-data now, so why would there be any permission problem?

Please help