system/database/DB_active_rec.php

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP 4.3.2 or newer
 *
 * @package		CodeIgniter
 * @author		ExpressionEngine Dev Team
 * @copyright	Copyright (c) 2008, EllisLab, Inc.
 * @license		http://codeigniter.com/user_guide/license.html
 * @link		http://codeigniter.com
 * @since		Version 1.0
 * @filesource
 */

// ------------------------------------------------------------------------

/**
 * Active Record Class
 *
 * This is the platform-independent base Active Record implementation class.
 *
 * @package		CodeIgniter
 * @subpackage	Drivers
 * @category	Database
 * @author		ExpressionEngine Dev Team
 * @link		http://codeigniter.com/user_guide/database/
 */
class CI_DB_active_record extends CI_DB_driver {

	var $ar_select				= array();
	var $ar_distinct			= FALSE;
	var $ar_from				= array();
	var $ar_join				= array();
	var $ar_where				= array();
	var $ar_like				= array();
	var $ar_groupby				= array();
	var $ar_having				= array();
	var $ar_limit				= FALSE;
	var $ar_offset				= FALSE;
	var $ar_order				= FALSE;
	var $ar_orderby				= array();
	var $ar_set					= array();	
	var $ar_wherein				= array();
	var $ar_aliased_tables		= array();
	var $ar_store_array			= array();
	
	// Active Record Caching variables
	var $ar_caching 			= FALSE;
	var $ar_cache_exists		= array();
	var $ar_cache_select		= array();
	var $ar_cache_from			= array();
	var $ar_cache_join			= array();
	var $ar_cache_where			= array();
	var $ar_cache_like			= array();
	var $ar_cache_groupby		= array();
	var $ar_cache_having		= array();
	var $ar_cache_limit			= FALSE;
	var $ar_cache_offset		= FALSE;
	var $ar_cache_order			= FALSE;
	var $ar_cache_orderby		= array();
	var $ar_cache_set			= array();	


	// --------------------------------------------------------------------

	/**
	 * Select
	 *
	 * Generates the SELECT portion of the query
	 *
	 * @access	public
	 * @param	string
	 * @return	object
	 */
	function select($select = '*', $escape = NULL)
	{
		// Set the global value if this was sepecified	
		if (is_bool($escape))
		{
			$this->_protect_identifiers = $escape;
		}
		
		if (is_string($select))
		{
			$select = explode(',', $select);
		}

		foreach ($select as $val)
		{
			$val = trim($val);

			if ($val != '')
			{
				$this->ar_select[] = $val;

				if ($this->ar_caching === TRUE)
				{
					$this->ar_cache_select[] = $val;
					$this->ar_cache_exists[] = 'select';
				}
			}
		}
		return $this;
	}

	// --------------------------------------------------------------------

	/**
	 * Select Max
	 *
	 * Generates a SELECT MAX(field) portion of a query
	 *
	 * @access	public
	 * @param	string	the field
	 * @param	string	an alias
	 * @return	object
	 */
	function select_max($select = '', $alias = '')
	{
		return $this->_max_min_avg_sum($select, $alias, 'MAX');
	}
		
	// --------------------------------------------------------------------

	/**
	 * Select Min
	 *
	 * Generates a SELECT MIN(field) portion of a query
	 *
	 * @access	public
	 * @param	string	the field
	 * @param	string	an alias
	 * @return	object
	 */
	function select_min($select = '', $alias = '')
	{
		return $this->_max_min_avg_sum($select, $alias, 'MIN');
	}

	// --------------------------------------------------------------------

	/**
	 * Select Average
	 *
	 * Generates a SELECT AVG(field) portion of a query
	 *
	 * @access	public
	 * @param	string	the field
	 * @param	string	an alias
	 * @return	object
	 */
	function select_avg($select = '', $alias = '')
	{
		return $this->_max_min_avg_sum($select, $alias, 'AVG');
	}

	// --------------------------------------------------------------------

	/**
	 * Select Sum
	 *
	 * Generates a SELECT SUM(field) portion of a query
	 *
	 * @access	public
	 * @param	string	the field
	 * @param	string	an alias
	 * @return	object
	 */
	function select_sum($select = '', $alias = '')
	{
		return $this->_max_min_avg_sum($select, $alias, 'SUM');
	}

	// --------------------------------------------------------------------

	/**
	 * Processing Function for the four functions above:
	 *
	 *	select_max()
	 *	select_min()
	 *	select_avg()
	 *  select_sum()
	 *	
	 * @access	public
	 * @param	string	the field
	 * @param	string	an alias
	 * @return	object
	 */
	function _max_min_avg_sum($select = '', $alias = '', $type = 'MAX')
	{
		if ( ! is_string($select) OR $select == '')
		{
			$this->display_error('db_invalid_query');
		}
	
		$type = strtoupper($type);
	
		if ( ! in_array($type, array('MAX', 'MIN', 'AVG', 'SUM')))
		{
			show_error('Invalid function type: '.$type);
		}
	
		if ($alias == '')
		{
			$alias = $this->_create_alias_from_table(trim($select));
		}
	
		$sql = $type.'('.$this->_protect_identifiers(trim($select)).') AS '.$alias;

		$this->ar_select[] = $sql;
		
		if ($this->ar_caching === TRUE)
		{
			$this->ar_cache_select[] = $sql;
			$this->ar_cache_exists[] = 'select';
		}
		
		return $this;
	}

	// --------------------------------------------------------------------

	/**
	 * Determines the alias name based on the table
	 *
	 * @access	private
	 * @param	string
	 * @return	string
	 */
	function _create_alias_from_table($item)
	{
		if (strpos($item, '.') !== FALSE)
		{
			return end(explode('.', $item));
		}
		
		return $item;
	}

	// --------------------------------------------------------------------

	/**
	 * DISTINCT
	 *
	 * Sets a flag which tells the query string compiler to add DISTINCT
	 *
	 * @access	public
	 * @param	bool
	 * @return	object
	 */
	function distinct($val = TRUE)
	{
		$this->ar_distinct = (is_bool($val)) ? $val : TRUE;
		return $this;
	}
	
	// --------------------------------------------------------------------

	/**
	 * From
	 *
	 * Generates the FROM portion of the query
	 *
	 * @access	public
	 * @param	mixed	can be a string or array
	 * @return	object
	 */
	function from($from)
	{
		foreach ((array)$from as $val)
		{
			// Extract any aliases that might exist.  We use this information
			// in the _protect_identifiers to know whether to add a table prefix 
			$this->_track_aliases($val);

			$this->ar_from[] = $this->_protect_identifiers($val, TRUE, NULL, FALSE);
			
			if ($this->ar_caching === TRUE)
			{
				$this->ar_cache_from[] = $this->_protect_identifiers($val, TRUE, NULL, FALSE);
				$this->ar_cache_exists[] = 'from';
			}
		}

		return $this;
	}

	// --------------------------------------------------------------------

	/**
	 * Join
	 *
	 * Generates the JOIN portion of the query
	 *
	 * @access	public
	 * @param	string
	 * @param	string	the join condition
	 * @param	string	the type of join
	 * @return	object
	 */
	function join($table, $cond, $type = '')
	{		
		if ($type != '')
		{
			$type = strtoupper(trim($type));

			if ( ! in_array($type, array('LEFT', 'RIGHT', 'OUTER', 'INNER', 'LEFT OUTER', 'RIGHT OUTER')))
			{
				$type = '';
			}
			else
			{
				$type .= ' ';
			}
		}

		// Extract any aliases that might exist.  We use this information
		// in the _protect_identifiers to know whether to add a table prefix 
		$this->_track_aliases($table);

		// Strip apart the condition and protect the identifiers
		if (preg_match('/([\w\.]+)([\W\s]+)(.+)/', $cond, $match))
		{
			$match[1] = $this->_protect_identifiers($match[1]);
			$match[3] = $this->_protect_identifiers($match[3]);
		
			$cond = $match[1].$match[2].$match[3];		
		}
		
		// Assemble the JOIN statement
		$join = $type.'JOIN '.$this->_protect_identifiers($table, TRUE, NULL, FALSE).' ON '.$cond;

		$this->ar_join[] = $join;
		if ($this->ar_caching === TRUE)
		{
			$this->ar_cache_join[] = $join;
			$this->ar_cache_exists[] = 'join';
		}

		return $this;
	}

	// --------------------------------------------------------------------

	/**
	 * Where
	 *
	 * Generates the WHERE portion of the query. Separates
	 * multiple calls with AND
	 *
	 * @access	public
	 * @param	mixed
	 * @param	mixed
	 * @return	object
	 */
	function where($key, $value = NULL, $escape = TRUE)
	{
		return $this->_where($key, $value, 'AND ', $escape);
	}
	
	// --------------------------------------------------------------------

	/**
	 * OR Where
	 *
	 * Generates the WHERE portion of the query. Separates
	 * multiple calls with OR
	 *
	 * @access	public
	 * @param	mixed
	 * @param	mixed
	 * @return	object
	 */
	function or_where($key, $value = NULL, $escape = TRUE)
	{
		return $this->_where($key, $value, 'OR ', $escape);
	}

	// --------------------------------------------------------------------

	/**
	 * orwhere() is an alias of or_where()
	 * this function is here for backwards compatibility, as
	 * orwhere() has been deprecated
	 */
	function orwhere($key, $value = NULL, $escape = TRUE)
	{
		return $this->or_where($key, $value, $escape);
	}

	// --------------------------------------------------------------------

	/**
	 * Where
	 *
	 * Called by where() or orwhere()
	 *
	 * @access	private
	 * @param	mixed
	 * @param	mixed
	 * @param	string
	 * @return	object
	 */
	function _where($key, $value = NULL, $type = 'AND ', $escape = NULL)
	{
		if ( ! is_array($key))
		{
			$key = array($key => $value);
		}
		
		// If the escape value was not set will will base it on the global setting
		if ( ! is_bool($escape))
		{
			$escape = $this->_protect_identifiers;
		}

		foreach ($key as $k => $v)
		{
			$prefix = (count($this->ar_where) == 0 AND count($this->ar_cache_where) == 0) ? '' : $type;

			if (is_null($v) && ! $this->_has_operator($k))
			{
				// value appears not to have been set, assign the test to IS NULL
				$k .= ' IS NULL';
			}
			
			if ( ! is_null($v))
			{
				if ($escape === TRUE)
				{
					$k = $this->_protect_identifiers($k, FALSE, $escape);
					
					$v = ' '.$this->escape($v);
				}

				if ( ! $this->_has_operator($k))
				{
					$k .= ' =';
				}
			}
			else
			{
				$k = $this->_protect_identifiers($k, FALSE, $escape);			
			}

			$this->ar_where[] = $prefix.$k.$v;
			
			if ($this->ar_caching === TRUE)
			{
				$this->ar_cache_where[] = $prefix.$k.$v;
				$this->ar_cache_exists[] = 'where';
			}
			
		}
		
		return $this;
	}

	// --------------------------------------------------------------------

	/**
	 * Where_in
	 *
	 * Generates a WHERE field IN ('item', 'item') SQL query joined with
	 * AND if appropriate
	 *
	 * @access	public
	 * @param	string	The field to search
	 * @param	array	The values searched on
	 * @return	object
	 */
	function where_in($key = NULL, $values = NULL)
	{
		return $this->_where_in($key, $values);
	}
	
	// --------------------------------------------------------------------

	/**
	 * Where_in_or
	 *
	 * Generates a WHERE field IN ('item', 'item') SQL query joined with
	 * OR if appropriate
	 *
	 * @access	public
	 * @param	string	The field to search
	 * @param	array	The values searched on
	 * @return	object
	 */
	function or_where_in($key = NULL, $values = NULL)
	{
		return $this->_where_in($key, $values, FALSE, 'OR ');
	}

	// --------------------------------------------------------------------

	/**
	 * Where_not_in
	 *
	 * Generates a WHERE field NOT IN ('item', 'item') SQL query joined
	 * with AND if appropriate
	 *
	 * @access	public
	 * @param	string	The field to search
	 * @param	array	The values searched on
	 * @return	object
	 */
	function where_not_in($key = NULL, $values = NULL)
	{
		return $this->_where_in($key, $values, TRUE);
	}
	
	// --------------------------------------------------------------------

	/**
	 * Where_not_in_or
	 *
	 * Generates a WHERE field NOT IN ('item', 'item') SQL query joined
	 * with OR if appropriate
	 *
	 * @access	public
	 * @param	string	The field to search
	 * @param	array	The values searched on
	 * @return	object
	 */
	function or_where_not_in($key = NULL, $values = NULL)
	{
		return $this->_where_in($key, $values, TRUE, 'OR ');
	}

	// --------------------------------------------------------------------

	/**
	 * Where_in
	 *
	 * Called by where_in, where_in_or, where_not_in, where_not_in_or
	 *
	 * @access	public
	 * @param	string	The field to search
	 * @param	array	The values searched on
	 * @param	boolean	If the statement would be IN or NOT IN
	 * @param	string	
	 * @return	object
	 */
	function _where_in($key = NULL, $values = NULL, $not = FALSE, $type = 'AND ')
	{
		if ($key === NULL OR $values === NULL)
		{
			return;
		}
		
		if ( ! is_array($values))
		{
			$values = array($values);
		}
		
		$not = ($not) ? ' NOT' : '';

		foreach ($values as $value)
		{
			$this->ar_wherein[] = $this->escape($value);
		}

		$prefix = (count($this->ar_where) == 0) ? '' : $type;
 
		$where_in = $prefix . $this->_protect_identifiers($key) . $not . " IN (" . implode(", ", $this->ar_wherein) . ") ";

		$this->ar_where[] = $where_in;
		if ($this->ar_caching === TRUE)
		{
			$this->ar_cache_where[] = $where_in;
			$this->ar_cache_exists[] = 'where';
		}

		// reset the array for multiple calls
		$this->ar_wherein = array();
		return $this;
	}
		
	// --------------------------------------------------------------------

	/**
	 * Like
	 *
	 * Generates a %LIKE% portion of the query. Separates
	 * multiple calls with AND
	 *
	 * @access	public
	 * @param	mixed
	 * @param	mixed
	 * @return	object
	 */
	function like($field, $match = '', $side = 'both')
	{
		return $this->_like($field, $match, 'AND ', $side);
	}

	// --------------------------------------------------------------------

	/**
	 * Not Like
	 *
	 * Generates a NOT LIKE portion of the query. Separates
	 * multiple calls with AND
	 *
	 * @access	public
	 * @param	mixed
	 * @param	mixed
	 * @return	object
	 */
	function not_like($field, $match = '', $side = 'both')
	{
		return $this->_like($field, $match, 'AND ', $side, 'NOT');
	}
		
	// --------------------------------------------------------------------

	/**
	 * OR Like
	 *
	 * Generates a %LIKE% portion of the query. Separates
	 * multiple calls with OR
	 *
	 * @access	public
	 * @param	mixed
	 * @param	mixed
	 * @return	object
	 */
	function or_like($field, $match = '', $side = 'both')
	{
		return $this->_like($field, $match, 'OR ', $side);
	}

	// --------------------------------------------------------------------

	/**
	 * OR Not Like
	 *
	 * Generates a NOT LIKE portion of the query. Separates
	 * multiple calls with OR
	 *
	 * @access	public
	 * @param	mixed
	 * @param	mixed
	 * @return	object
	 */
	function or_not_like($field, $match = '', $side = 'both')
	{
		return $this->_like($field, $match, 'OR ', $side, 'NOT');
	}
	
	// --------------------------------------------------------------------

	/**
	 * orlike() is an alias of or_like()
	 * this function is here for backwards compatibility, as
	 * orlike() has been deprecated
	 */
	function orlike($field, $match = '', $side = 'both')
	{
		return $this->or_like($field, $match, $side);
	}
	
	// --------------------------------------------------------------------

	/**
	 * Like
	 *
	 * Called by like() or orlike()
	 *
	 * @access	private
	 * @param	mixed
	 * @param	mixed
	 * @param	string
	 * @return	object
	 */
	function _like($field, $match = '', $type = 'AND ', $side = 'both', $not = '')
	{
		if ( ! is_array($field))
		{
			$field = array($field => $match);
		}
 	
		foreach ($field as $k => $v)
		{
			$k = $this->_protect_identifiers($k);

			$prefix = (count($this->ar_like) == 0) ? '' : $type;

			$v = $this->escape_str($v);

			if ($side == 'before')
			{
				$like_statement = $prefix." $k $not LIKE '%{$v}'";
			}
			elseif ($side == 'after')
			{
				$like_statement = $prefix." $k $not LIKE '{$v}%'";
			}
			else
			{
				$like_statement = $prefix." $k $not LIKE '%{$v}%'";
			}
			
			$this->ar_like[] = $like_statement;
			if ($this->ar_caching === TRUE)
			{
				$this->ar_cache_like[] = $like_statement;
				$this->ar_cache_exists[] = 'like';
			}
			
		}
		return $this;
	}
	
	// --------------------------------------------------------------------

	/**
	 * GROUP BY
	 *
	 * @access	public
	 * @param	string
	 * @return	object
	 */
	function group_by($by)
	{
		if (is_string($by))
		{
			$by = explode(',', $by);
		}
	
		foreach ($by as $val)
		{
			$val = trim($val);
		
			if ($val != '')
			{
				$this->ar_groupby[] = $this->_protect_identifiers($val);
				
				if ($this->ar_caching === TRUE)
				{
					$this->ar_cache_groupby[] = $this->_protect_identifiers($val);
					$this->ar_cache_exists[] = 'groupby';
				}
			}
		}
		return $this;
	}

	// --------------------------------------------------------------------

	/**
	 * groupby() is an alias of group_by()
	 * this function is here for backwards compatibility, as
	 * groupby() has been deprecated
	 */
	function groupby($by)
	{
		return $this->group_by($by);
	}	

	// --------------------------------------------------------------------

	/**
	 * Sets the HAVING value
	 *
	 * Separates multiple calls with AND
	 *
	 * @access	public
	 * @param	string
	 * @param	string
	 * @return	object
	 */
	function having($key, $value = '', $escape = TRUE)
	{
		return $this->_having($key, $value, 'AND ', $escape);
	}

	// --------------------------------------------------------------------

	/**
	 * orhaving() is an alias of or_having()
	 * this function is here for backwards compatibility, as
	 * orhaving() has been deprecated
	 */

	function orhaving($key, $value = '', $escape = TRUE)
	{
		return $this->or_having($key, $value, $escape);
	}	
	// --------------------------------------------------------------------

	/**
	 * Sets the OR HAVING value
	 *
	 * Separates multiple calls with OR
	 *
	 * @access	public
	 * @param	string
	 * @param	string
	 * @return	object
	 */
	function or_having($key, $value = '', $escape = TRUE)
	{
		return $this->_having($key, $value, 'OR ', $escape);
	}
	
	// --------------------------------------------------------------------

	/**
	 * Sets the HAVING values
	 *
	 * Called by having() or or_having()
	 *
	 * @access	private
	 * @param	string
	 * @param	string
	 * @return	object
	 */
	function _having($key, $value = '', $type = 'AND ', $escape = TRUE)
	{
		if ( ! is_array($key))
		{
			$key = array($key => $value);
		}
	
		foreach ($key as $k => $v)
		{
			$prefix = (count($this->ar_having) == 0) ? '' : $type;

			if ($escape === TRUE)
			{
				$k = $this->_protect_identifiers($k);
			}

			if ( ! $this->_has_operator($k))
			{
				$k .= ' = ';
			}

			if ($v != '')
			{
				$v = ' '.$this->escape_str($v);
			}
			
			$this->ar_having[] = $prefix.$k.$v;
			if ($this->ar_caching === TRUE)
			{
				$this->ar_cache_having[] = $prefix.$k.$v;
				$this->ar_cache_exists[] = 'having';
			}
		}
		
		return $this;
	}
	
	// --------------------------------------------------------------------

	/**
	 * Sets the ORDER BY value
	 *
	 * @access	public
	 * @param	string
	 * @param	string	direction: asc or desc
	 * @return	object
	 */
	function order_by($orderby, $direction = '')
	{
		if (strtolower($direction) == 'random')
		{
			$orderby = ''; // Random results want or don't need a field name
			$direction = $this->_random_keyword;
		}
		elseif (trim($direction) != '')
		{
			$direction = (in_array(strtoupper(trim($direction)), array('ASC', 'DESC'), TRUE)) ? ' '.$direction : ' ASC';
		}
		
		$orderby_statement = $this->_protect_identifiers($orderby).$direction;
		
		$this->ar_orderby[] = $orderby_statement;
		if ($this->ar_caching === TRUE)
		{
			$this->ar_cache_orderby[] = $orderby_statement;
			$this->ar_cache_exists[] = 'orderby';
		}

		return $this;
	}
	
	// --------------------------------------------------------------------

	/**
	 * orderby() is an alias of order_by()
	 * this function is here for backwards compatibility, as
	 * orderby() has been deprecated
	 */
	function orderby($orderby, $direction = '')
	{
		return $this->order_by($orderby, $direction);
	}
	
	// --------------------------------------------------------------------

	/**
	 * Sets the LIMIT value
	 *
	 * @access	public
	 * @param	integer	the limit value
	 * @param	integer	the offset value
	 * @return	object
	 */
	function limit($value, $offset = '')
	{
		$this->ar_limit = $value;
		if ($this->ar_caching === TRUE)
		{
			$this->ar_cache_limit[] = $value;
			$this->ar_cache_exists[] = 'limit';
		}

		if ($offset != '')
		{
			$this->ar_offset = $offset;
			if ($this->ar_caching === TRUE)
			{
				$this->ar_cache_offset[] = $offset;
				$this->ar_cache_exists[] = 'limit';
			}
		}
		
		return $this;
	}
	
	// --------------------------------------------------------------------

	/**
	 * Sets the OFFSET value
	 *
	 * @access	public
	 * @param	integer	the offset value
	 * @return	object
	 */
	function offset($offset)
	{
		$this->ar_offset = $offset;
		if ($this->ar_caching === TRUE)
		{
			$this->ar_cache_offset[] = $offset;
			$this->ar_cache_exists[] = 'offset';
		}
			
		return $this;
	}
	
	// --------------------------------------------------------------------

	/**
	 * The "set" function.  Allows key/value pairs to be set for inserting or updating
	 *
	 * @access	public
	 * @param	mixed
	 * @param	string
	 * @param	boolean
	 * @return	object
	 */
	function set($key, $value = '', $escape = TRUE)
	{
		$key = $this->_object_to_array($key);
	
		if ( ! is_array($key))
		{
			$key = array($key => $value);
		}	

		foreach ($key as $k => $v)
		{
			if ($escape === FALSE)
			{
				$this->ar_set[$this->_protect_identifiers($k)] = $v;
				
				if ($this->ar_caching === TRUE)
				{
					$this->ar_cache_offset[$this->_protect_identifiers($k)] = $v;
					$this->ar_cache_exists[] = 'offset';
				}
			}
			else
			{
				$this->ar_set[$this->_protect_identifiers($k)] = $this->escape($v);
				
				if ($this->ar_caching === TRUE)
				{
					$this->ar_cache_offset[$this->_protect_identifiers($k)] = $this->escape($v);
					$this->ar_cache_exists[] = 'offset';
				}
			}
		}
		
		return $this;
	}
	
	// --------------------------------------------------------------------

	/**
	 * Get
	 *
	 * Compiles the select statement based on the other functions called
	 * and runs the query
	 *
	 * @access	public
	 * @param	string	the table
	 * @param	string	the limit clause
	 * @param	string	the offset clause
	 * @return	object
	 */
	function get($table = '', $limit = null, $offset = null)
	{
		if ($table != '')
		{
			$this->_track_aliases($table);
			$this->from($table);
		}
		
		if ( ! is_null($limit))
		{
			$this->limit($limit, $offset);
		}
			
		$sql = $this->_compile_select();

		$result = $this->query($sql);
		$this->_reset_select();
		return $result;
	}

	/**
	 * "Count All Results" query
	 *
	 * Generates a platform-specific query string that counts all records 
	 * returned by an Active Record query.
	 *
	 * @access	public
	 * @param	string
	 * @return	string
	 */
	function count_all_results($table = '')
	{
		if ($table != '')
		{
			$this->_track_aliases($table);
			$this->from($table);
		}
		
		$sql = $this->_compile_select($this->_count_string . $this->_protect_identifiers('numrows'));

		$query = $this->query($sql);
		$this->_reset_select();
	
		if ($query->num_rows() == 0)
		{
			return '0';
		}

		$row = $query->row();
		return $row->numrows;
	}

	// --------------------------------------------------------------------

	/**
	 * Get_Where
	 *
	 * Allows the where clause, limit and offset to be added directly
	 *
	 * @access	public
	 * @param	string	the where clause
	 * @param	string	the limit clause
	 * @param	string	the offset clause
	 * @return	object
	 */
	function get_where($table = '', $where = null, $limit = null, $offset = null)
	{
		if ($table != '')
		{
			$this->from($table);
		}

		if ( ! is_null($where))
		{
			$this->where($where);
		}
		
		if ( ! is_null($limit))
		{
			$this->limit($limit, $offset);
		}
			
		$sql = $this->_compile_select();

		$result = $this->query($sql);
		$this->_reset_select();
		return $result;
	}

	// --------------------------------------------------------------------

	/**
	 * getwhere() is an alias of get_where()
	 * this function is here for backwards compatibility, as
	 * getwhere() has been deprecated
	 */
	function getwhere($table = '', $where = null, $limit = null, $offset = null)
	{
		return $this->get_where($table, $where, $limit, $offset);
	}
	
	// --------------------------------------------------------------------

	/**
	 * Insert
	 *
	 * Compiles an insert string and runs the query
	 *
	 * @access	public
	 * @param	string	the table to retrieve the results from
	 * @param	array	an associative array of insert values
	 * @return	object
	 */
	function insert($table = '', $set = NULL)
	{
		if ( ! is_null($set))
		{
			$this->set($set);
		}
	
		if (count($this->ar_set) == 0)
		{
			if ($this->db_debug)
			{
				return $this->display_error('db_must_use_set');
			}
			return FALSE;
		}

		if ($table == '')
		{
			if ( ! isset($this->ar_from[0]))
			{
				if ($this->db_debug)
				{
					return $this->display_error('db_must_set_table');
				}
				return FALSE;
			}
			
			$table = $this->ar_from[0];
		}

		$sql = $this->_insert($this->_protect_identifiers($table, TRUE, NULL, FALSE), array_keys($this->ar_set), array_values($this->ar_set));
		
		$this->_reset_write();
		return $this->query($sql);		
	}
	
	// --------------------------------------------------------------------

	/**
	 * Update
	 *
	 * Compiles an update string and runs the query
	 *
	 * @access	public
	 * @param	string	the table to retrieve the results from
	 * @param	array	an associative array of update values
	 * @param	mixed	the where clause
	 * @return	object
	 */
	function update($table = '', $set = NULL, $where = NULL, $limit = NULL)
	{
		if ( ! is_null($set))
		{
			$this->set($set);
		}
	
		if (count($this->ar_set) == 0)
		{
			if ($this->db_debug)
			{
				return $this->display_error('db_must_use_set');
			}
			return FALSE;
		}

		if ($table == '')
		{
			if ( ! isset($this->ar_from[0]))
			{
				if ($this->db_debug)
				{
					return $this->display_error('db_must_set_table');
				}
				return FALSE;
			}
			
			$table = $this->ar_from[0];
		}
		
		if ($where != NULL)
		{
			$this->where($where);
		}

		if ($limit != NULL)
		{
			$this->limit($limit);
		}
		
		$sql = $this->_update($this->_protect_identifiers($table, TRUE, NULL, FALSE), $this->ar_set, $this->ar_where, $this->ar_orderby, $this->ar_limit);
		
		$this->_reset_write();
		return $this->query($sql);
	}

	// --------------------------------------------------------------------

	/**
	 * Empty Table
	 *
	 * Compiles a delete string and runs "DELETE FROM table"
	 *
	 * @access	public
	 * @param	string	the table to empty
	 * @return	object
	 */
	function empty_table($table = '')
	{
		if ($table == '')
		{
			if ( ! isset($this->ar_from[0]))
			{
				if ($this->db_debug)
				{
					return $this->display_error('db_must_set_table');
				}
				return FALSE;
			}

			$table = $this->ar_from[0];
		}
		else
		{
			$table = $this->_protect_identifiers($table, TRUE, NULL, FALSE);
		}

		$sql = $this->_delete($table);

		$this->_reset_write();
		
		return $this->query($sql);
	}

	// --------------------------------------------------------------------

	/**
	 * Truncate
	 *
	 * Compiles a truncate string and runs the query
	 * If the database does not support the truncate() command
	 * This function maps to "DELETE FROM table"
	 *
	 * @access	public
	 * @param	string	the table to truncate
	 * @return	object
	 */
	function truncate($table = '')
	{
		if ($table == '')
		{
			if ( ! isset($this->ar_from[0]))
			{
				if ($this->db_debug)
				{
					return $this->display_error('db_must_set_table');
				}
				return FALSE;
			}

			$table = $this->ar_from[0];
		}
		else
		{
			$table = $this->_protect_identifiers($table, TRUE, NULL, FALSE);
		}

		$sql = $this->_truncate($table);

		$this->_reset_write();
		
		return $this->query($sql);
	}
	
	// --------------------------------------------------------------------

	/**
	 * Delete
	 *
	 * Compiles a delete string and runs the query
	 *
	 * @access	public
	 * @param	mixed	the table(s) to delete from. String or array
	 * @param	mixed	the where clause
	 * @param	mixed	the limit clause
	 * @param	boolean
	 * @return	object
	 */
	function delete($table = '', $where = '', $limit = NULL, $reset_data = TRUE)
	{
		if ($table == '')
		{
			if ( ! isset($this->ar_from[0]))
			{
				if ($this->db_debug)
				{
					return $this->display_error('db_must_set_table');
				}
				return FALSE;
			}

			$table = $this->ar_from[0];
		}
		elseif (is_array($table))
		{
			foreach($table as $single_table)
			{
				$this->delete($single_table, $where, $limit, FALSE);
			}

			$this->_reset_write();
			return;
		}
		else
		{
			$table = $this->_protect_identifiers($table, TRUE, NULL, FALSE);
		}

		if ($where != '')
		{
			$this->where($where);
		}

		if ($limit != NULL)
		{
			$this->limit($limit);
		}

		if (count($this->ar_where) == 0 && count($this->ar_like) == 0)
		{
			if ($this->db_debug)
			{
				return $this->display_error('db_del_must_use_where');
			}

			return FALSE;
		}		

		$sql = $this->_delete($table, $this->ar_where, $this->ar_like, $this->ar_limit);

		if ($reset_data)
		{
			$this->_reset_write();
		}
		
		return $this->query($sql);
	}

	// --------------------------------------------------------------------

	/**
	 * DB Prefix
	 *
	 * Prepends a database prefix if one exists in configuration
	 *
	 * @access	public
	 * @param	string	the table
	 * @return	string
	 */
	function dbprefix($table = '')
	{
		if ($table == '')
		{
			$this->display_error('db_table_name_required');
		}

		return $this->dbprefix.$table;
	}

	// --------------------------------------------------------------------

	/**
	 * Track Aliases
	 *
	 * Used to track SQL statements written with aliased tables.
	 *
	 * @access	private
	 * @param	string	The table to inspect
	 * @return	string
	 */	
	function _track_aliases($table)
	{
		if (is_array($table))
		{
			foreach ($table as $t)
			{
				$this->_track_aliases($t);
			}
			return;
		}
		
		// Does the string contain a comma?  If so, we need to separate
		// the string into discreet statements
		if (strpos($table, ',') !== FALSE)
		{
			return $this->_track_aliases(explode(',', $table));
		}
	
		// if a table alias is used we can recognize it by a space
		if (strpos($table, " ") !== FALSE)
		{
			// if the alias is written with the AS keyword, remove it
			$table = preg_replace('/ AS /i', ' ', $table);
			
			// Grab the alias
			$table = trim(strrchr($table, " "));
			
			// Store the alias, if it doesn't already exist
			if ( ! in_array($table, $this->ar_aliased_tables))
			{
				$this->ar_aliased_tables[] = $table;
			}
		}
	}

	// --------------------------------------------------------------------

	/**
	 * Compile the SELECT statement
	 *
	 * Generates a query string based on which functions were used.
	 * Should not be called directly.  The get() function calls it.
	 *
	 * @access	private
	 * @return	string
	 */
	function _compile_select($select_override = FALSE)
	{
		$this->_merge_cache();

		// ----------------------------------------------------------------
		
		// Write the "select" portion of the query

		if ($select_override !== FALSE)
		{
			$sql = $select_override;
		}
		else
		{
			$sql = ( ! $this->ar_distinct) ? 'SELECT ' : 'SELECT DISTINCT ';
		
			if (count($this->ar_select) == 0)
			{
				$sql .= '*';		
			}
			else
			{				
				// Cycle through the "select" portion of the query and prep each column name.
				// The reason we protect identifiers here rather then in the select() function
				// is because until the user calls the from() function we don't know if there are aliases
				foreach ($this->ar_select as $key => $val)
				{
					$this->ar_select[$key] = $this->_protect_identifiers($val);
				}
				
				$sql .= implode(', ', $this->ar_select);
			}
		}

		// ----------------------------------------------------------------
		
		// Write the "FROM" portion of the query

		if (count($this->ar_from) > 0)
		{
			$sql .= "\nFROM ";

			$sql .= $this->_from_tables($this->ar_from);
		}

		// ----------------------------------------------------------------
		
		// Write the "JOIN" portion of the query

		if (count($this->ar_join) > 0)
		{
			$sql .= "\n";

			$sql .= implode("\n", $this->ar_join);
		}

		// ----------------------------------------------------------------
		
		// Write the "WHERE" portion of the query

		if (count($this->ar_where) > 0 OR count($this->ar_like) > 0)
		{
			$sql .= "\n";

			$sql .= "WHERE ";
		}

		$sql .= implode("\n", $this->ar_where);

		// ----------------------------------------------------------------
		
		// Write the "LIKE" portion of the query
	
		if (count($this->ar_like) > 0)
		{
			if (count($this->ar_where) > 0)
			{
				$sql .= "\nAND ";
			}

			$sql .= implode("\n", $this->ar_like);
		}

		// ----------------------------------------------------------------
		
		// Write the "GROUP BY" portion of the query
	
		if (count($this->ar_groupby) > 0)
		{
			$sql .= "\nGROUP BY ";
			
			$sql .= implode(', ', $this->ar_groupby);
		}

		// ----------------------------------------------------------------
		
		// Write the "HAVING" portion of the query
		
		if (count($this->ar_having) > 0)
		{
			$sql .= "\nHAVING ";
			$sql .= implode("\n", $this->ar_having);
		}

		// ----------------------------------------------------------------
		
		// Write the "ORDER BY" portion of the query

		if (count($this->ar_orderby) > 0)
		{
			$sql .= "\nORDER BY ";
			$sql .= implode(', ', $this->ar_orderby);
			
			if ($this->ar_order !== FALSE)
			{
				$sql .= ($this->ar_order == 'desc') ? ' DESC' : ' ASC';
			}		
		}

		// ----------------------------------------------------------------
		
		// Write the "LIMIT" portion of the query
		
		if (is_numeric($this->ar_limit))
		{
			$sql .= "\n";
			$sql = $this->_limit($sql, $this->ar_limit, $this->ar_offset);
		}

		return $sql;
	}

	// --------------------------------------------------------------------

	/**
	 * Object to Array
	 *
	 * Takes an object as input and converts the class variables to array key/vals
	 *
	 * @access	public
	 * @param	object
	 * @return	array
	 */
	function _object_to_array($object)
	{
		if ( ! is_object($object))
		{
			return $object;
		}
		
		$array = array();
		foreach (get_object_vars($object) as $key => $val)
		{
			// There are some built in keys we need to ignore for this conversion
			if ( ! is_object($val) && ! is_array($val) && $key != '_parent_name' && $key != '_ci_scaffolding' && $key != '_ci_scaff_table')
			{
				$array[$key] = $val;
			}
		}
	
		return $array;
	}
	
	// --------------------------------------------------------------------

	/**
	 * Start Cache
	 *
	 * Starts AR caching
	 *
	 * @access	public
	 * @return	void
	 */		
	function start_cache()
	{
		$this->ar_caching = TRUE;
	}

	// --------------------------------------------------------------------

	/**
	 * Stop Cache
	 *
	 * Stops AR caching
	 *
	 * @access	public
	 * @return	void
	 */		
	function stop_cache()
	{
		$this->ar_caching = FALSE;
	}

	// --------------------------------------------------------------------

	/**
	 * Flush Cache
	 *
	 * Empties the AR cache
	 *
	 * @access	public
	 * @return	void
	 */	
	function flush_cache()
	{	
		$ar_reset_items = array(
									'ar_cache_select'	=> array(), 
									'ar_cache_from'		=> array(), 
									'ar_cache_join'		=> array(),
									'ar_cache_where'	=> array(), 
									'ar_cache_like'		=> array(), 
									'ar_cache_groupby'	=> array(), 
									'ar_cache_having'	=> array(), 
									'ar_cache_orderby'	=> array(), 
									'ar_cache_set'		=> array(),
									'ar_cache_exists'	=> array()
								);

		$this->_reset_run($ar_reset_items);	
	}

	// --------------------------------------------------------------------

	/**
	 * Merge Cache
	 *
	 * When called, this function merges any cached AR arrays with 
	 * locally called ones.
	 *
	 * @access	private
	 * @return	void
	 */
	function _merge_cache()
	{
		if (count($this->ar_cache_exists) == 0)
		{
			return;
		}

		foreach ($this->ar_cache_exists as $val)
		{
			$ar_variable	= 'ar_'.$val;
			$ar_cache_var	= 'ar_cache_'.$val;

			if (count($this->$ar_cache_var) == 0)
			{
				continue;
			}

			$this->$ar_variable = array_unique(array_merge($this->$ar_cache_var, $this->$ar_variable));
		}

		// If we are "protecting identifiers" we need to examine the "from"
		// portion of the query to determine if there are any aliases
		if ($this->_protect_identifiers === TRUE AND count($this->ar_cache_from) > 0)
		{
			$this->_track_aliases($this->ar_from);
		}
	}

	// --------------------------------------------------------------------

	/**
	 * Resets the active record values.  Called by the get() function
	 *
	 * @access	private
	 * @param	array	An array of fields to reset
	 * @return	void
	 */
	function _reset_run($ar_reset_items)
	{
		foreach ($ar_reset_items as $item => $default_value)
		{
			if ( ! in_array($item, $this->ar_store_array))
			{
				$this->$item = $default_value;
			}
		}
	}

	// --------------------------------------------------------------------

	/**
	 * Resets the active record values.  Called by the get() function
	 *
	 * @access	private
	 * @return	void
	 */
	function _reset_select()
	{
		$ar_reset_items = array(
								'ar_select'			=> array(), 
								'ar_from'			=> array(), 
								'ar_join'			=> array(), 
								'ar_where'			=> array(), 
								'ar_like'			=> array(), 
								'ar_groupby'		=> array(), 
								'ar_having'			=> array(), 
								'ar_orderby'		=> array(), 
								'ar_wherein'		=> array(), 
								'ar_aliased_tables'	=> array(),
								'ar_distinct'		=> FALSE, 
								'ar_limit'			=> FALSE, 
								'ar_offset'			=> FALSE, 
								'ar_order'			=> FALSE,
							);
		
		$this->_reset_run($ar_reset_items);
	}
	
	// --------------------------------------------------------------------

	/**
	 * Resets the active record "write" values.
	 *
	 * Called by the insert() update() and delete() functions
	 *
	 * @access	private
	 * @return	void
	 */
	function _reset_write()
	{	
		$ar_reset_items = array(
								'ar_set'		=> array(), 
								'ar_from'		=> array(), 
								'ar_where'		=> array(), 
								'ar_like'		=> array(),
								'ar_orderby'	=> array(), 
								'ar_limit'		=> FALSE, 
								'ar_order'		=> FALSE
								);

		$this->_reset_run($ar_reset_items);
	}
	
}

/* End of file DB_active_rec.php */
/* Location: ./system/database/DB_active_rec.php */