Your /opt/Apache/htdocs/peerpower/local_config.php file is missing a declaration for $logger_logFile.
Here is a sample local_config.php file:
<?php // database connection string $peepagg_dsn = "mysql://user:password@server/databasename"; // where to log messages and errors. note that this file must be writeable by the web server. $logger_logFile = "$path_prefix/log/pa.log"; // url of the "web" directory $base_url = "http://%network_name%.peerpower.com"; // the constant part of the domain (such that if we chop this off the server name, we should get the network name). $domain_suffix = "peerpower.com"; ?>
(except with your own database details).