For developer is very convenient to see PHP source code simply adding extension phps instead of php.
If you would like to access control to the source code, here is how to do it.
For example, everyone could see page www.example.com/page.php,
but only user joe will be able to see www.example.com/page.phps
RewriteRule (.*).phps$ /protected/sourcecode-phps.php [L]
AuthType BasicAuthName "Protected Access"
require user joe
else echo "PHP source file not found: $uri";