There is a tiny bug in the Aggregator class when using the flush() function. The reference to $connections should be $this->connections.
Change:
public function flush() {
$result = false;
for ($i = 0; $i < count($connections); $i++) {
if ($this->connections[$i]->flush()) {
$result = true;
}
}
return $result;
}
To:
public function flush() {
$result = false;
for ($i = 0; $i < count($this->connections); $i++) {
if ($this->connections[$i]->flush()) {
$result = true;
}
}
return $result;
}