Return value

Bool

Full documentation

Set status value to 'New', if row is being saved for the first time and status is empty:

if ( $Order->isNew() ){
    $Order->status->setDefault('New');
}

Create or open a Invoice for customer. Set default values, if new.

$Invoice = $this->get('page','invoice')->findUnique(
    'customer' ,$customer->getId(),
    'status'   ,'New'
);

if ( $Invoice->isNew() ){
    $Invoice->invoice_date = $this->get('date');
    $Invoice->due_date     = $Invoice->invoice_date->getDate()->addDays(14);
}