Deny Access To configuration file using php scripts

Hello i have a web server and i have a major problem

some of my users are trying to find my pass for my mysql database.

the first thing they do is a
system ('cat /var/www/path to config file');
inside a php script

my problem is to deny this file from being read throu the script since
the apache deamon runs as nobody
and it has to have read permision to the configuration file.

my users have shell acount and can create files in the public_html folder.
any help?
snif!

thanks in advance.
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