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<?phpclass tx extends orm{	protected $lines;		public function __construct()	{		parent::__construct('tx');		$this->lines = array();	}		public function load($id)	{		parent::load($id);				// load children		$db = my_db::get_instance();		$res = $db->query('select id from tx_line where tx_id=?', $id);		while($row = $res->fetch())		{			$line = new orm('tx_line');			$line->load($row['id']);			$this->line_add($line);		}	}		protected function line_add($line)	{		$id = count($this->lines);		$this->lines[$id] = array($line, 1);		return $id;	}		public function line_new()	{		return $this->line_add(new orm('tx_line'));	}		public function line_list()	{		$result = array();		foreach($this->lines as $k => $v) if($v[1]) $result[] = $k;		return $result;	}		public function line_get($line) { return $this->lines[$line][0]; }		public function line_delete($line)	{		$this->lines[$line][1] = 0;	}		public function save()	{		$dtc = dtc::get_instance();		$in_tx = $dtc->in_tx();		if(!$in_tx) $dtc->begin();				try		{			$db = my_db::get_instance();			parent::save();						foreach(array_keys($this->lines) as $k)			{				if($this->lines[$k][1])				{					$this->lines[$k][0]->tx_id = $this->data['id'];					$this->lines[$k][0]->save();				}				else				{					$this->lines[$k][0]->delete();				}			}						$check = $db->query('SELECT (COUNT(*) > 1) num, (SUM(amount) = 0) total FROM tx_line WHERE tx_id = ?', $this->data['id'])->fetch();						if(!$check['num']) throw new Exception('Transaction must involve at least one account.');			if(!$check['total']) throw new Exception('Transaction must total to 0.');		}		catch(Exception $ex)		{			if(!$in_tx) $dtc->rollback();			throw $ex;		}				if(!$in_tx) $dtc->commit();				foreach(array_keys($this->lines) as $k)		{			if(!$this->lines[$k][1])			{				unset($this->lines[$k]);			}		}				return $this->data['id'];	}}?>