public function getNumberProspectsPerDay($maxDays = 30)
    {
    	$select = $this->tableGateway->getSql()->select();

    	$select->columns(array(new \Zend\Db\Sql\Expression('COUNT("pros_id") AS nb'), "pros_contact_date"));
    	$select->group("pros_contact_date");
    	$select->limit($maxDays);
    	
    	$resultSet = $this->tableGateway->selectWith($select);
    
    	return $resultSet;
    }