Zend offers different logging possibilities. I won't present them all.

But basics remain. By default there are timestamp, message, priority and priorityName entries. If you want to log your own entry you have to deal with event array. To add a custom field use setEventItem() method.

$db; //was initialized sooner it holds our database adapter
$dbTableName; //initialized sooner, the name of our table

$columnMapping = array(
 'timestamp' => 'timestamp',
 'priorityName' => 'priorityName',
 'priorityLevel' => 'priority',
 'userIp' => 'userip',
 'userHost' => 'userhost',
 'message' => 'message'
 );

//register writer
$dbWriter = new Zend_Log_Writer_Db();
//register logger
$logger = new Zend_Log( $dbWriter );

//add custom params to log
$logger->setEventItem('userIp', $userIp);
$logger->setEventItem('userHost', $userHost;

$logger->log("something to log ...");