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<?php
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/**
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 * TDbDataReader class file
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 *
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 * @author Qiang Xue <qiang.xue@gmail.com>
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 * @link http://www.pradosoft.com/
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 * @copyright Copyright &copy; 2005-2008 PradoSoft
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 * @license http://www.pradosoft.com/license/
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 * @version $Id: TDbDataReader.php 2541 2008-10-21 15:05:13Z qiang.xue $
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 * @package System.Data
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 */
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/**
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 * TDbDataReader class.
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 *
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 * TDbDataReader represents a forward-only stream of rows from a query result set.
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 *
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 * To read the current row of data, call {@link read}. The method {@link readAll}
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 * returns all the rows in a single array.
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 *
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 * One can also retrieve the rows of data in TDbDataReader by using foreach:
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 * <code>
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 * foreach($reader as $row)
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 *     // $row represents a row of data
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 * </code>
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 * Since TDbDataReader is a forward-only stream, you can only traverse it once.
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 *
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 * It is possible to use a specific mode of data fetching by setting
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 * {@link setFetchMode FetchMode}. See {@link http://www.php.net/manual/en/function.PDOStatement-setFetchMode.php}
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 * for more details.
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 *
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 * @author Qiang Xue <qiang.xue@gmail.com>
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 * @version $Id: TDbDataReader.php 2541 2008-10-21 15:05:13Z qiang.xue $
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 * @package System.Data
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 * @since 3.0
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 */
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class TDbDataReader extends TComponent implements Iterator
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{
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	private $_statement;
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	private $_closed=false;
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	private $_row;
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	private $_index=-1;
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	/**
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	 * Constructor.
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	 * @param TDbCommand the command generating the query result
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	 */
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	public function __construct(TDbCommand $command)
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	{
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		$this->_statement=$command->getPdoStatement();
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		$this->_statement->setFetchMode(PDO::FETCH_ASSOC);
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	}
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	/**
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	 * Binds a column to a PHP variable.
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	 * When rows of data are being fetched, the corresponding column value
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	 * will be set in the variable. Note, the fetch mode must include PDO::FETCH_BOUND.
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	 * @param mixed Number of the column (1-indexed) or name of the column
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	 * in the result set. If using the column name, be aware that the name
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	 * should match the case of the column, as returned by the driver.
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	 * @param mixed Name of the PHP variable to which the column will be bound.
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	 * @param int Data type of the parameter
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	 * @see http://www.php.net/manual/en/function.PDOStatement-bindColumn.php
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	 */
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	public function bindColumn($column, &$value, $dataType=null)
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	{
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		if($dataType===null)
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			$this->_statement->bindColumn($column,$value);
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		else
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			$this->_statement->bindColumn($column,$value,$dataType);
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	}
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	/**
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	 * @see http://www.php.net/manual/en/function.PDOStatement-setFetchMode.php
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	 */
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	public function setFetchMode($mode)
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	{
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		$params=func_get_args();
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		call_user_func_array(array($this->_statement,'setFetchMode'),$params);
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	}
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	/**
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	 * Advances the reader to the next row in a result set.
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	 * @return array|false the current row, false if no more row available
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	 */
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	public function read()
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	{
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		return $this->_statement->fetch();
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	}
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	/**
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	 * Returns a single column from the next row of a result set.
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	 * @param int zero-based column index
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	 * @return mixed|false the column of the current row, false if no more row available
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	 */
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	public function readColumn($columnIndex)
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	{
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		return $this->_statement->fetchColumn($columnIndex);
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	}
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	/**
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	 * Returns a single column from the next row of a result set.
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	 * @param string class name of the object to be created and populated
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	 * @param array list of column names whose values are to be passed as parameters in the constructor of the class being created
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	 * @return mixed|false the populated object, false if no more row of data available
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	 */
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	public function readObject($className,$fields)
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	{
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		return $this->_statement->fetchObject($className,$fields);
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	}
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	/**
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	 * Reads the whole result set into an array.
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	 * @return array the result set (each array element represents a row of data).
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	 * An empty array will be returned if the result contains no row.
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	 */
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	public function readAll()
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	{
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		return $this->_statement->fetchAll();
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	}
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	/**
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	 * Advances the reader to the next result when reading the results of a batch of statements.
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	 * This method is only useful when there are multiple result sets
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	 * returned by the query. Not all DBMS support this feature.
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	 */
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	public function nextResult()
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	{
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		return $this->_statement->nextRowset();
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	}
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	/**
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	 * Closes the reader.
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	 * Any further data reading will result in an exception.
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	 */
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	public function close()
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	{
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		$this->_statement->closeCursor();
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		$this->_closed=true;
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	}
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	/**
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	 * @return boolean whether the reader is closed or not.
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	 */
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	public function getIsClosed()
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	{
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		return $this->_closed;
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	}
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	/**
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	 * @return int number of rows contained in the result.
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	 * Note, most DBMS may not give a meaningful count.
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	 * In this case, use "SELECT COUNT(*) FROM tableName" to obtain the number of rows.
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	 */
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	public function getRowCount()
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	{
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		return $this->_statement->rowCount();
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	}
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	/**
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	 * @return int the number of columns in the result set.
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	 * Note, even there's no row in the reader, this still gives correct column number.
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	 */
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	public function getColumnCount()
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	{
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		return $this->_statement->columnCount();
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	}
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	/**
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	 * Resets the iterator to the initial state.
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	 * This method is required by the interface Iterator.
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	 * @throws TDbException if this method is invoked twice
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	 */
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	public function rewind()
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	{
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		if($this->_index<0)
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		{
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			$this->_row=$this->_statement->fetch();
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			$this->_index=0;
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		}
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		else
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			throw new TDbException('dbdatareader_rewind_invalid');
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	}
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	/**
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	 * Returns the index of the current row.
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	 * This method is required by the interface Iterator.
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	 * @return integer the index of the current row.
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	 */
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	public function key()
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	{
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		return $this->_index;
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	}
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	/**
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	 * Returns the current row.
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	 * This method is required by the interface Iterator.
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	 * @return mixed the current row.
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	 */
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	public function current()
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	{
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		return $this->_row;
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	}
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	/**
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	 * Moves the internal pointer to the next row.
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	 * This method is required by the interface Iterator.
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	 */
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	public function next()
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	{
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		$this->_row=$this->_statement->fetch();
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		$this->_index++;
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	}
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	/**
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	 * Returns whether there is a row of data at current position.
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	 * This method is required by the interface Iterator.
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	 * @return boolean whether there is a row of data at current position.
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	 */
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	public function valid()
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	{
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		return $this->_row!==false;
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	}
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}
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