ci-bonfire / Sprint

system/database/DB_driver.php

<?php

For compatibility and reusability of your code, PSR1 recommends that a file should introduce either new symbols (like classes, functions, etc.) or have side-effects (like outputting something, or including other files), but not both at the same time. The first symbol is defined on line 53 and the first side effect is on line 38.

/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2015, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package	CodeIgniter
 * @author	EllisLab Dev Team
 * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (http://ellislab.com/)
 * @copyright	Copyright (c) 2014 - 2015, British Columbia Institute of Technology (http://bcit.ca/)
 * @license	http://opensource.org/licenses/MIT	MIT License
 * @link	http://codeigniter.com
 * @since	Version 1.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * Database Driver Class
 *
 * This is the platform-independent base DB implementation class.
 * This class will not be called directly. Rather, the adapter
 * class for the specific database will extend and instantiate it.
 *
 * @package		CodeIgniter
 * @subpackage	Drivers
 * @category	Database
 * @author		EllisLab Dev Team
 * @link		http://codeigniter.com/user_guide/database/
 */
abstract class CI_DB_driver {

	/**
	 * Data Source Name / Connect string
	 *
	 * @var	string
	 */
	public $dsn;

	/**
	 * Username
	 *
	 * @var	string
	 */
	public $username;

	/**
	 * Password
	 *
	 * @var	string
	 */
	public $password;

	/**
	 * Hostname
	 *
	 * @var	string
	 */
	public $hostname;

	/**
	 * Database name
	 *
	 * @var	string
	 */
	public $database;

	/**
	 * Database driver
	 *
	 * @var	string
	 */
	public $dbdriver		= 'mysqli';

	/**
	 * Sub-driver
	 *
	 * @used-by	CI_DB_pdo_driver
	 * @var	string
	 */
	public $subdriver;

	/**
	 * Table prefix
	 *
	 * @var	string
	 */
	public $dbprefix		= '';

	/**
	 * Character set
	 *
	 * @var	string
	 */
	public $char_set		= 'utf8';

	/**
	 * Collation
	 *
	 * @var	string
	 */
	public $dbcollat		= 'utf8_general_ci';

	/**
	 * Encryption flag/data
	 *
	 * @var	mixed
	 */
	public $encrypt			= FALSE;

	/**
	 * Swap Prefix
	 *
	 * @var	string
	 */
	public $swap_pre		= '';

	/**
	 * Database port
	 *
	 * @var	int
	 */
	public $port			= '';

	/**
	 * Persistent connection flag
	 *
	 * @var	bool
	 */
	public $pconnect		= FALSE;

	/**
	 * Connection ID
	 *
	 * @var	object|resource
	 */
	public $conn_id			= FALSE;

	/**
	 * Result ID
	 *
	 * @var	object|resource
	 */
	public $result_id		= FALSE;

	/**
	 * Debug flag
	 *
	 * Whether to display error messages.
	 *
	 * @var	bool
	 */
	public $db_debug		= FALSE;

	/**
	 * Benchmark time
	 *
	 * @var	int
	 */
	public $benchmark		= 0;

	/**
	 * Executed queries count
	 *
	 * @var	int
	 */
	public $query_count		= 0;

	/**
	 * Bind marker
	 *
	 * Character used to identify values in a prepared statement.
	 *
	 * @var	string
	 */
	public $bind_marker		= '?';

	/**
	 * Save queries flag
	 *
	 * Whether to keep an in-memory history of queries for debugging purposes.
	 *
	 * @var	bool
	 */
	public $save_queries		= TRUE;

	/**
	 * Queries list
	 *
	 * @see	CI_DB_driver::$save_queries
	 * @var	string[]
	 */
	public $queries			= array();

	/**
	 * Query times
	 *
	 * A list of times that queries took to execute.
	 *
	 * @var	array
	 */
	public $query_times		= array();

	/**
	 * Data cache
	 *
	 * An internal generic value cache.
	 *
	 * @var	array
	 */
	public $data_cache		= array();

	/**
	 * Transaction enabled flag
	 *
	 * @var	bool
	 */
	public $trans_enabled		= TRUE;

	/**
	 * Strict transaction mode flag
	 *
	 * @var	bool
	 */
	public $trans_strict		= TRUE;

	/**
	 * Transaction depth level
	 *
	 * @var	int
	 */
	protected $_trans_depth		= 0;

	/**
	 * Transaction status flag
	 *
	 * Used with transactions to determine if a rollback should occur.
	 *
	 * @var	bool
	 */
	protected $_trans_status	= TRUE;

	/**
	 * Transaction failure flag
	 *
	 * Used with transactions to determine if a transaction has failed.
	 *
	 * @var	bool
	 */
	protected $_trans_failure	= FALSE;

	/**
	 * Cache On flag
	 *
	 * @var	bool
	 */
	public $cache_on		= FALSE;

	/**
	 * Cache directory path
	 *
	 * @var	bool
	 */
	public $cachedir		= '';

	/**
	 * Cache auto-delete flag
	 *
	 * @var	bool
	 */
	public $cache_autodel		= FALSE;

	/**
	 * DB Cache object
	 *
	 * @see	CI_DB_cache
	 * @var	object
	 */
	public $CACHE;

	/**
	 * Protect identifiers flag
	 *
	 * @var	bool
	 */
	protected $_protect_identifiers		= TRUE;

	/**
	 * List of reserved identifiers
	 *
	 * Identifiers that must NOT be escaped.
	 *
	 * @var	string[]
	 */
	protected $_reserved_identifiers	= array('*');

	/**
	 * Identifier escape character
	 *
	 * @var	string
	 */
	protected $_escape_char = '"';

	/**
	 * ESCAPE statement string
	 *
	 * @var	string
	 */
	protected $_like_escape_str = " ESCAPE '%s' ";

	/**
	 * ESCAPE character
	 *
	 * @var	string
	 */
	protected $_like_escape_chr = '!';

	/**
	 * ORDER BY random keyword
	 *
	 * @var	array
	 */
	protected $_random_keyword = array('RAND()', 'RAND(%d)');

	/**
	 * COUNT string
	 *
	 * @used-by	CI_DB_driver::count_all()
	 * @used-by	CI_DB_query_builder::count_all_results()
	 *
	 * @var	string
	 */
	protected $_count_string = 'SELECT COUNT(*) AS ';

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

	/**
	 * Class constructor
	 *
	 * @param	array	$params
	 * @return	void
	 */
	public function __construct($params)
	{
		if (is_array($params))
		{
			foreach ($params as $key => $val)
			{
				$this->$key = $val;
			}
		}

		log_message('info', 'Database Driver Class Initialized');
	}

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

	/**
	 * Initialize Database Settings
	 *
	 * @return	bool
	 */
	public function initialize()
	{
		/* If an established connection is available, then there's
		 * no need to connect and select the database.
		 *
		 * Depending on the database driver, conn_id can be either
		 * boolean TRUE, a resource or an object.
		 */
		if ($this->conn_id)
		{
			return TRUE;
		}

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

		// Connect to the database and set the connection ID
		$this->conn_id = $this->db_connect($this->pconnect);

		// No connection resource? Check if there is a failover else throw an error
		if ( ! $this->conn_id)
		{
			// Check if there is a failover set
			if ( ! empty($this->failover) && is_array($this->failover))
			{
				// Go over all the failovers
				foreach ($this->failover as $failover)
				{
					// Replace the current settings with those of the failover
					foreach ($failover as $key => $val)
					{
						$this->$key = $val;
					}

					// Try to connect
					$this->conn_id = $this->db_connect($this->pconnect);

					// If a connection is made break the foreach loop
					if ($this->conn_id)
					{
						break;
					}
				}
			}

			// We still don't have a connection?
			if ( ! $this->conn_id)
			{
				log_message('error', 'Unable to connect to the database');

				if ($this->db_debug)
				{
					$this->display_error('db_unable_to_connect');
				}

				return FALSE;
			}
		}

		// Now we set the character set and that's all
		return $this->db_set_charset($this->char_set);
	}

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

	/**
	 * DB connect
	 *
	 * This is just a dummy method that all drivers will override.
	 *
	 * @return	mixed
	 */
	public function db_connect()
	{
		return TRUE;
	}

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

	/**
	 * Persistent database connection
	 *
	 * @return	mixed
	 */
	public function db_pconnect()
	{
		return $this->db_connect(TRUE);
	}

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

	/**
	 * Reconnect
	 *
	 * Keep / reestablish the db connection if no queries have been
	 * sent for a length of time exceeding the server's idle timeout.
	 *
	 * This is just a dummy method to allow drivers without such
	 * functionality to not declare it, while others will override it.
	 *
	 * @return	void
	 */
	public function reconnect()
	{
	}

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

	/**
	 * Select database
	 *
	 * This is just a dummy method to allow drivers without such
	 * functionality to not declare it, while others will override it.
	 *
	 * @return	bool
	 */
	public function db_select()
	{
		return TRUE;
	}

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

	/**
	 * Last error
	 *
	 * @return	array
	 */
	public function error()
	{
		return array('code' => NULL, 'message' => NULL);
	}

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

	/**
	 * Set client character set
	 *
	 * @param	string
	 * @return	bool
	 */
	public function db_set_charset($charset)
	{
		if (method_exists($this, '_db_set_charset') && ! $this->_db_set_charset($charset))
		{
			log_message('error', 'Unable to set database connection charset: '.$charset);

			if ($this->db_debug)
			{
				$this->display_error('db_unable_to_set_charset', $charset);
			}

			return FALSE;
		}

		return TRUE;
	}

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

	/**
	 * The name of the platform in use (mysql, mssql, etc...)
	 *
	 * @return	string
	 */
	public function platform()
	{
		return $this->dbdriver;
	}

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

	/**
	 * Database version number
	 *
	 * Returns a string containing the version of the database being used.
	 * Most drivers will override this method.
	 *
	 * @return	string
	 */
	public function version()
	{
		if (isset($this->data_cache['version']))
		{
			return $this->data_cache['version'];
		}

		if (FALSE === ($sql = $this->_version()))
		{
			return ($this->db_debug) ? $this->display_error('db_unsupported_function') : FALSE;

The expression $this->db_debug ? $this->display_error('db_unsupported_function') : FALSE; of type string|false adds false to the return on line 573 which is incompatible with the return type documented by CI_DB_driver::version of type string. It seems like you forgot to handle an error condition.

		}

		$query = $this->query($sql)->row();
		return $this->data_cache['version'] = $query->ver;
	}

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

	/**
	 * Version number query string
	 *
	 * @return	string
	 */
	protected function _version()
	{
		return 'SELECT VERSION() AS ver';
	}

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

	/**
	 * Execute the query
	 *
	 * Accepts an SQL string as input and returns a result object upon
	 * successful execution of a "read" type query. Returns boolean TRUE
	 * upon successful execution of a "write" type query. Returns boolean
	 * FALSE upon failure, and if the $db_debug variable is set to TRUE
	 * will raise an error.
	 *
	 * @param	string	$sql
	 * @param	array	$binds = FALSE		An array of binding data
	 * @param	bool	$return_object = NULL
	 * @return	mixed
	 */
	public function query($sql, $binds = FALSE, $return_object = NULL)
	{
		if ($sql === '')
		{
			log_message('error', 'Invalid query: '.$sql);
			return ($this->db_debug) ? $this->display_error('db_invalid_query') : FALSE;
		}
		elseif ( ! is_bool($return_object))
		{
			$return_object = ! $this->is_write_type($sql);
		}

		// Verify table prefix and replace if necessary
		if ($this->dbprefix !== '' && $this->swap_pre !== '' && $this->dbprefix !== $this->swap_pre)
		{
			$sql = preg_replace('/(\W)'.$this->swap_pre.'(\S+?)/', '\\1'.$this->dbprefix.'\\2', $sql);
		}

		// Compile binds if needed
		if ($binds !== FALSE)
		{
			$sql = $this->compile_binds($sql, $binds);
		}

		// Is query caching enabled? If the query is a "read type"
		// we will load the caching class and return the previously
		// cached query if it exists
		if ($this->cache_on === TRUE && $return_object === TRUE && $this->_cache_init())
		{
			$this->load_rdriver();
			if (FALSE !== ($cache = $this->CACHE->read($sql)))
			{
				return $cache;
			}
		}

		// Save the query for debugging
		if ($this->save_queries === TRUE)
		{
			$this->queries[] = $sql;
		}

		// Start the Query Timer
		$time_start = microtime(TRUE);

		// Run the Query
		if (FALSE === ($this->result_id = $this->simple_query($sql)))
		{
			if ($this->save_queries === TRUE)
			{
				$this->query_times[] = 0;
			}

			// This will trigger a rollback if transactions are being used
			if ($this->_trans_depth !== 0)
			{
				$this->_trans_status = FALSE;
			}

			// Grab the error now, as we might run some additional queries before displaying the error
			$error = $this->error();

			// Log errors
			log_message('error', 'Query error: '.$error['message'].' - Invalid query: '.$sql);

			if ($this->db_debug)
			{
				// We call this function in order to roll-back queries
				// if transactions are enabled. If we don't call this here
				// the error message will trigger an exit, causing the
				// transactions to remain in limbo.
				if ($this->_trans_depth !== 0)
				{
					do
					{
						$trans_depth = $this->_trans_depth;
						$this->trans_complete();
						if ($trans_depth === $this->_trans_depth)
						{
							log_message('error', 'Database: Failure during an automated transaction commit/rollback!');
							break;
						}
					}
					while ($this->_trans_depth !== 0);
				}

				// Display errors
				return $this->display_error(array('Error Number: '.$error['code'], $error['message'], $sql));

array('Error Number: ' . $error['code'], $error['message'], $sql) is of type array<integer,string|null,{"0":"string","1":"null","2":"string"}>, but the function expects a string.

			}

			return FALSE;
		}

		// Stop and aggregate the query time results
		$time_end = microtime(TRUE);
		$this->benchmark += $time_end - $time_start;

		if ($this->save_queries === TRUE)
		{
			$this->query_times[] = $time_end - $time_start;
		}

		// Increment the query counter
		$this->query_count++;

		// Will we have a result object instantiated? If not - we'll simply return TRUE
		if ($return_object !== TRUE)
		{
			// If caching is enabled we'll auto-cleanup any existing files related to this particular URI
			if ($this->cache_on === TRUE && $this->cache_autodel === TRUE && $this->_cache_init())
			{
				$this->CACHE->delete();
			}

			return TRUE;
		}

		// Load and instantiate the result driver
		$driver		= $this->load_rdriver();
		$RES		= new $driver($this);

		// Is query caching enabled? If so, we'll serialize the
		// result object and save it to a cache file.
		if ($this->cache_on === TRUE && $this->_cache_init())
		{
			// We'll create a new instance of the result object
			// only without the platform specific driver since
			// we can't use it with cached data (the query result
			// resource ID won't be any good once we've cached the
			// result object, so we'll have to compile the data
			// and save it)
			$CR = new CI_DB_result($this);
			$CR->result_object	= $RES->result_object();
			$CR->result_array	= $RES->result_array();
			$CR->num_rows		= $RES->num_rows();

			// Reset these since cached objects can not utilize resource IDs.
			$CR->conn_id		= NULL;
			$CR->result_id		= NULL;

			$this->CACHE->write($sql, $CR);
		}

		return $RES;
	}

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

	/**
	 * Load the result drivers
	 *
	 * @return	string	the name of the result class
	 */
	public function load_rdriver()
	{
		$driver = 'CI_DB_'.$this->dbdriver.'_result';

		if ( ! class_exists($driver, FALSE))
		{
			require_once(BASEPATH.'database/DB_result.php');
			require_once(BASEPATH.'database/drivers/'.$this->dbdriver.'/'.$this->dbdriver.'_result.php');
		}

		return $driver;
	}

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

	/**
	 * Simple Query
	 * This is a simplified version of the query() function. Internally
	 * we only use it when running transaction commands since they do
	 * not require all the features of the main query() function.
	 *
	 * @param	string	the sql query
	 * @return	mixed
	 */
	public function simple_query($sql)
	{
		if ( ! $this->conn_id)
		{
			if ( ! $this->initialize())
			{
				return FALSE;
			}
		}

		return $this->_execute($sql);
	}

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

	/**
	 * Disable Transactions
	 * This permits transactions to be disabled at run-time.
	 *
	 * @return	void
	 */
	public function trans_off()
	{
		$this->trans_enabled = FALSE;
	}

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

	/**
	 * Enable/disable Transaction Strict Mode
	 *
	 * When strict mode is enabled, if you are running multiple groups of
	 * transactions, if one group fails all subsequent groups will be
	 * rolled back.
	 *
	 * If strict mode is disabled, each group is treated autonomously,
	 * meaning a failure of one group will not affect any others
	 *
	 * @param	bool	$mode = TRUE
	 * @return	void
	 */
	public function trans_strict($mode = TRUE)
	{
		$this->trans_strict = is_bool($mode) ? $mode : TRUE;
	}

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

	/**
	 * Start Transaction
	 *
	 * @param	bool	$test_mode = FALSE
	 * @return	bool
	 */
	public function trans_start($test_mode = FALSE)
	{
		if ( ! $this->trans_enabled)
		{
			return FALSE;
		}

		return $this->trans_begin($test_mode);
	}

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

	/**
	 * Complete Transaction
	 *
	 * @return	bool
	 */
	public function trans_complete()
	{
		if ( ! $this->trans_enabled)
		{
			return FALSE;
		}

		// The query() function will set this flag to FALSE in the event that a query failed
		if ($this->_trans_status === FALSE OR $this->_trans_failure === TRUE)
		{
			$this->trans_rollback();

			// If we are NOT running in strict mode, we will reset
			// the _trans_status flag so that subsequent groups of
			// transactions will be permitted.
			if ($this->trans_strict === FALSE)
			{
				$this->_trans_status = TRUE;
			}

			log_message('debug', 'DB Transaction Failure');
			return FALSE;
		}

		return $this->trans_commit();
	}

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

	/**
	 * Lets you retrieve the transaction flag to determine if it has failed
	 *
	 * @return	bool
	 */
	public function trans_status()
	{
		return $this->_trans_status;
	}

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

	/**
	 * Begin Transaction
	 *
	 * @param	bool	$test_mode
	 * @return	bool
	 */
	public function trans_begin($test_mode = FALSE)
	{
		if ( ! $this->trans_enabled)
		{
			return FALSE;
		}
		// When transactions are nested we only begin/commit/rollback the outermost ones
		elseif ($this->_trans_depth > 0)
		{
			$this->_trans_depth++;
			return TRUE;
		}

		// Reset the transaction failure flag.
		// If the $test_mode flag is set to TRUE transactions will be rolled back
		// even if the queries produce a successful result.
		$this->_trans_failure = ($test_mode === TRUE);

		if ($this->_trans_begin())
		{
			$this->_trans_depth++;
			return TRUE;
		}

		return FALSE;
	}

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

	/**
	 * Commit Transaction
	 *
	 * @return	bool
	 */
	public function trans_commit()
	{
		if ( ! $this->trans_enabled OR $this->_trans_depth === 0)

Using logical operators such as or instead of || is generally not recommended.

		{
			return FALSE;
		}
		// When transactions are nested we only begin/commit/rollback the outermost ones
		elseif ($this->_trans_depth > 1 OR $this->_trans_commit())
		{
			$this->_trans_depth--;
			return TRUE;
		}

		return FALSE;
	}

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

	/**
	 * Rollback Transaction
	 *
	 * @return	bool
	 */
	public function trans_rollback()
	{
		if ( ! $this->trans_enabled OR $this->_trans_depth === 0)

Using logical operators such as or instead of || is generally not recommended.

		{
			return FALSE;
		}
		// When transactions are nested we only begin/commit/rollback the outermost ones
		elseif ($this->_trans_depth > 1 OR $this->_trans_rollback())
		{
			$this->_trans_depth--;
			return TRUE;
		}

		return FALSE;
	}

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

	/**
	 * Compile Bindings
	 *
	 * @param	string	the sql statement
	 * @param	array	an array of bind data
	 * @return	string
	 */
	public function compile_binds($sql, $binds)
	{
		if (empty($binds) OR empty($this->bind_marker) OR strpos($sql, $this->bind_marker) === FALSE)
		{
			return $sql;
		}
		elseif ( ! is_array($binds))
		{
			$binds = array($binds);
			$bind_count = 1;
		}
		else
		{
			// Make sure we're using numeric keys
			$binds = array_values($binds);
			$bind_count = count($binds);
		}

		// We'll need the marker length later
		$ml = strlen($this->bind_marker);

		// Make sure not to replace a chunk inside a string that happens to match the bind marker
		if ($c = preg_match_all("/'[^']*'/i", $sql, $matches))
		{
			$c = preg_match_all('/'.preg_quote($this->bind_marker, '/').'/i',
				str_replace($matches[0],
					str_replace($this->bind_marker, str_repeat(' ', $ml), $matches[0]),
					$sql, $c),
				$matches, PREG_OFFSET_CAPTURE);

			// Bind values' count must match the count of markers in the query
			if ($bind_count !== $c)
			{
				return $sql;
			}
		}
		elseif (($c = preg_match_all('/'.preg_quote($this->bind_marker, '/').'/i', $sql, $matches, PREG_OFFSET_CAPTURE)) !== $bind_count)
		{
			return $sql;
		}

		do
		{
			$c--;
			$escaped_value = $this->escape($binds[$c]);
			if (is_array($escaped_value))
			{
				$escaped_value = '('.implode(',', $escaped_value).')';
			}
			$sql = substr_replace($sql, $escaped_value, $matches[0][$c][1], $ml);
		}
		while ($c !== 0);

		return $sql;
	}

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

	/**
	 * Determines if a query is a "write" type.
	 *
	 * @param	string	An SQL query string
	 * @return	bool
	 */
	public function is_write_type($sql)
	{
		return (bool) preg_match('/^\s*"?(SET|INSERT|UPDATE|DELETE|REPLACE|CREATE|DROP|TRUNCATE|LOAD|COPY|ALTER|RENAME|GRANT|REVOKE|LOCK|UNLOCK|REINDEX)\s/i', $sql);
	}

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

	/**
	 * Calculate the aggregate query elapsed time
	 *
	 * @param	int	The number of decimal places
	 * @return	string
	 */
	public function elapsed_time($decimals = 6)
	{
		return number_format($this->benchmark, $decimals);
	}

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

	/**
	 * Returns the total number of queries
	 *
	 * @return	int
	 */
	public function total_queries()
	{
		return $this->query_count;
	}

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

	/**
	 * Returns the last query that was executed
	 *
	 * @return	string
	 */
	public function last_query()
	{
		return end($this->queries);
	}

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

	/**
	 * "Smart" Escape String
	 *
	 * Escapes data based on type
	 * Sets boolean and null types
	 *
	 * @param	string
	 * @return	mixed
	 */
	public function escape($str)
	{
		if (is_array($str))
		{
			$str = array_map(array(&$this, 'escape'), $str);
			return $str;
		}
		elseif (is_string($str) OR (is_object($str) && method_exists($str, '__toString')))
		{
			return "'".$this->escape_str($str)."'";
		}
		elseif (is_bool($str))
		{
			return ($str === FALSE) ? 0 : 1;
		}
		elseif ($str === NULL)
		{
			return 'NULL';
		}

		return $str;
	}

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

	/**
	 * Escape String
	 *
	 * @param	string|string[]	$str	Input string
	 * @param	bool	$like	Whether or not the string will be used in a LIKE condition
	 * @return	string
	 */
	public function escape_str($str, $like = FALSE)
	{
		if (is_array($str))
		{
			foreach ($str as $key => $val)
			{
				$str[$key] = $this->escape_str($val, $like);
			}

			return $str;
		}

		$str = $this->_escape_str($str);

		// escape LIKE condition wildcards
		if ($like === TRUE)
		{
			return str_replace(
				array($this->_like_escape_chr, '%', '_'),
				array($this->_like_escape_chr.$this->_like_escape_chr, $this->_like_escape_chr.'%', $this->_like_escape_chr.'_'),
				$str
			);
		}

		return $str;
	}

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

	/**
	 * Escape LIKE String
	 *
	 * Calls the individual driver for platform
	 * specific escaping for LIKE conditions
	 *
	 * @param	string|string[]
	 * @return	mixed
	 */
	public function escape_like_str($str)
	{
		return $this->escape_str($str, TRUE);
	}

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

	/**
	 * Platform-dependant string escape
	 *
	 * @param	string
	 * @return	string
	 */
	protected function _escape_str($str)
	{
		return str_replace("'", "''", remove_invisible_characters($str));
	}

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

	/**
	 * Primary
	 *
	 * Retrieves the primary key. It assumes that the row in the first
	 * position is the primary key
	 *
	 * @param	string	$table	Table name
	 * @return	string
	 */
	public function primary($table)
	{
		$fields = $this->list_fields($table);
		return is_array($fields) ? current($fields) : FALSE;
	}

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

	/**
	 * "Count All" query
	 *
	 * Generates a platform-specific query string that counts all records in
	 * the specified database
	 *
	 * @param	string
	 * @return	int
	 */
	public function count_all($table = '')
	{
		if ($table === '')
		{
			return 0;
		}

		$query = $this->query($this->_count_string.$this->escape_identifiers('numrows').' FROM '.$this->protect_identifiers($table, TRUE, NULL, FALSE));
		if ($query->num_rows() === 0)
		{
			return 0;
		}

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

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

	/**
	 * Returns an array of table names
	 *
	 * @param	string	$constrain_by_prefix = FALSE
	 * @return	array
	 */
	public function list_tables($constrain_by_prefix = FALSE)
	{
		// Is there a cached result?
		if (isset($this->data_cache['table_names']))
		{
			return $this->data_cache['table_names'];
		}

		if (FALSE === ($sql = $this->_list_tables($constrain_by_prefix)))
		{
			return ($this->db_debug) ? $this->display_error('db_unsupported_function') : FALSE;
		}

		$this->data_cache['table_names'] = array();
		$query = $this->query($sql);

		foreach ($query->result_array() as $row)

This code seems to be duplicated across your project.

		{
			// Do we know from which column to get the table name?
			if ( ! isset($key))
			{
				if (isset($row['table_name']))
				{
					$key = 'table_name';
				}
				elseif (isset($row['TABLE_NAME']))
				{
					$key = 'TABLE_NAME';
				}
				else
				{
					/* We have no other choice but to just get the first element's key.
					 * Due to array_shift() accepting its argument by reference, if
					 * E_STRICT is on, this would trigger a warning. So we'll have to
					 * assign it first.
					 */
					$key = array_keys($row);
					$key = array_shift($key);
				}
			}

			$this->data_cache['table_names'][] = $row[$key];
		}

		return $this->data_cache['table_names'];
	}

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

	/**
	 * Determine if a particular table exists
	 *
	 * @param	string	$table_name
	 * @return	bool
	 */
	public function table_exists($table_name)
	{
		return in_array($this->protect_identifiers($table_name, TRUE, FALSE, FALSE), $this->list_tables());
	}

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

	/**
	 * Fetch Field Names
	 *
	 * @param	string	$table	Table name
	 * @return	array
	 */
	public function list_fields($table)
	{
		// Is there a cached result?
		if (isset($this->data_cache['field_names'][$table]))
		{
			return $this->data_cache['field_names'][$table];
		}

		if (FALSE === ($sql = $this->_list_columns($table)))
		{
			return ($this->db_debug) ? $this->display_error('db_unsupported_function') : FALSE;
		}

		$query = $this->query($sql);
		$this->data_cache['field_names'][$table] = array();

		foreach ($query->result_array() as $row)

This code seems to be duplicated across your project.

		{
			// Do we know from where to get the column's name?
			if ( ! isset($key))
			{
				if (isset($row['column_name']))
				{
					$key = 'column_name';
				}
				elseif (isset($row['COLUMN_NAME']))
				{
					$key = 'COLUMN_NAME';
				}
				else
				{
					// We have no other choice but to just get the first element's key.
					$key = key($row);
				}
			}

			$this->data_cache['field_names'][$table][] = $row[$key];
		}

		return $this->data_cache['field_names'][$table];
	}

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

	/**
	 * Determine if a particular field exists
	 *
	 * @param	string
	 * @param	string
	 * @return	bool
	 */
	public function field_exists($field_name, $table_name)
	{
		return in_array($field_name, $this->list_fields($table_name));
	}

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

	/**
	 * Returns an object with field data
	 *
	 * @param	string	$table	the table name
	 * @return	array
	 */
	public function field_data($table)
	{
		$query = $this->query($this->_field_data($this->protect_identifiers($table, TRUE, NULL, FALSE)));
		return ($query) ? $query->field_data() : FALSE;
	}

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

	/**
	 * Escape the SQL Identifiers
	 *
	 * This function escapes column and table names
	 *
	 * @param	mixed
	 * @return	mixed
	 */
	public function escape_identifiers($item)
	{
		if ($this->_escape_char === '' OR empty($item) OR in_array($item, $this->_reserved_identifiers))
		{
			return $item;
		}
		elseif (is_array($item))
		{
			foreach ($item as $key => $value)
			{
				$item[$key] = $this->escape_identifiers($value);
			}

			return $item;
		}
		// Avoid breaking functions and literal values inside queries
		elseif (ctype_digit($item) OR $item[0] === "'" OR ($this->_escape_char !== '"' && $item[0] === '"') OR strpos($item, '(') !== FALSE)
		{
			return $item;
		}

		static $preg_ec = array();

		if (empty($preg_ec))
		{
			if (is_array($this->_escape_char))
			{
				$preg_ec = array(
					preg_quote($this->_escape_char[0], '/'),
					preg_quote($this->_escape_char[1], '/'),
					$this->_escape_char[0],
					$this->_escape_char[1]
				);
			}
			else
			{
				$preg_ec[0] = $preg_ec[1] = preg_quote($this->_escape_char, '/');
				$preg_ec[2] = $preg_ec[3] = $this->_escape_char;
			}
		}

		foreach ($this->_reserved_identifiers as $id)
		{
			if (strpos($item, '.'.$id) !== FALSE)
			{
				return preg_replace('/'.$preg_ec[0].'?([^'.$preg_ec[1].'\.]+)'.$preg_ec[1].'?\./i', $preg_ec[2].'$1'.$preg_ec[3].'.', $item);
			}
		}

		return preg_replace('/'.$preg_ec[0].'?([^'.$preg_ec[1].'\.]+)'.$preg_ec[1].'?(\.)?/i', $preg_ec[2].'$1'.$preg_ec[3].'$2', $item);
	}

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

	/**
	 * Generate an insert string
	 *
	 * @param	string	the table upon which the query will be performed
	 * @param	array	an associative array data of key/values
	 * @return	string
	 */
	public function insert_string($table, $data)
	{
		$fields = $values = array();

		foreach ($data as $key => $val)
		{
			$fields[] = $this->escape_identifiers($key);
			$values[] = $this->escape($val);
		}

		return $this->_insert($this->protect_identifiers($table, TRUE, NULL, FALSE), $fields, $values);
	}

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

	/**
	 * Insert statement
	 *
	 * Generates a platform-specific insert string from the supplied data
	 *
	 * @param	string	the table name
	 * @param	array	the insert keys
	 * @param	array	the insert values
	 * @return	string
	 */
	protected function _insert($table, $keys, $values)
	{
		return 'INSERT INTO '.$table.' ('.implode(', ', $keys).') VALUES ('.implode(', ', $values).')';
	}

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

	/**
	 * Generate an update string
	 *
	 * @param	string	the table upon which the query will be performed
	 * @param	array	an associative array data of key/values
	 * @param	mixed	the "where" statement
	 * @return	string
	 */
	public function update_string($table, $data, $where)
	{
		if (empty($where))
		{
			return FALSE;
		}

		$this->where($where);

		$fields = array();
		foreach ($data as $key => $val)
		{
			$fields[$this->protect_identifiers($key)] = $this->escape($val);
		}

		$sql = $this->_update($this->protect_identifiers($table, TRUE, NULL, FALSE), $fields);
		$this->_reset_write();
		return $sql;
	}

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

	/**
	 * Update statement
	 *
	 * Generates a platform-specific update string from the supplied data
	 *
	 * @param	string	the table name
	 * @param	array	the update data
	 * @return	string
	 */
	protected function _update($table, $values)
	{
		foreach ($values as $key => $val)
		{
			$valstr[] = $key.' = '.$val;
		}

		return 'UPDATE '.$table.' SET '.implode(', ', $valstr)
			.$this->_compile_wh('qb_where')
			.$this->_compile_order_by()
			.($this->qb_limit ? ' LIMIT '.$this->qb_limit : '');
	}

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

	/**
	 * Tests whether the string has an SQL operator
	 *
	 * @param	string
	 * @return	bool
	 */
	protected function _has_operator($str)
	{
		return (bool) preg_match('/(<|>|!|=|\sIS NULL|\sIS NOT NULL|\sEXISTS|\sBETWEEN|\sLIKE|\sIN\s*\(|\s)/i', trim($str));
	}

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

	/**
	 * Returns the SQL string operator
	 *
	 * @param	string
	 * @return	string
	 */
	protected function _get_operator($str)
	{
		static $_operators;

		if (empty($_operators))
		{
			$_les = ($this->_like_escape_str !== '')
				? '\s+'.preg_quote(trim(sprintf($this->_like_escape_str, $this->_like_escape_chr)), '/')
				: '';
			$_operators = array(
				'\s*(?:<|>|!)?=\s*',             // =, <=, >=, !=
				'\s*<>?\s*',                     // <, <>
				'\s*>\s*',                       // >
				'\s+IS NULL',                    // IS NULL
				'\s+IS NOT NULL',                // IS NOT NULL
				'\s+EXISTS\s*\([^\)]+\)',        // EXISTS(sql)
				'\s+NOT EXISTS\s*\([^\)]+\)',    // NOT EXISTS(sql)
				'\s+BETWEEN\s+',                 // BETWEEN value AND value
				'\s+IN\s*\([^\)]+\)',            // IN(list)
				'\s+NOT IN\s*\([^\)]+\)',        // NOT IN (list)

38% of this comment could be valid code. Did you maybe forget this after debugging?

				'\s+LIKE\s+\S.*('.$_les.')?',    // LIKE 'expr'[ ESCAPE '%s']

40% of this comment could be valid code. Did you maybe forget this after debugging?

				'\s+NOT LIKE\s+\S.*('.$_les.')?' // NOT LIKE 'expr'[ ESCAPE '%s']
			);

		}

		return preg_match('/'.implode('|', $_operators).'/i', $str, $match)
			? $match[0] : FALSE;
	}

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

	/**
	 * Enables a native PHP function to be run, using a platform agnostic wrapper.
	 *
	 * @param	string	$function	Function name
	 * @return	mixed
	 */
	public function call_function($function)
	{
		$driver = ($this->dbdriver === 'postgre') ? 'pg_' : $this->dbdriver.'_';

		if (FALSE === strpos($driver, $function))
		{
			$function = $driver.$function;
		}

		if ( ! function_exists($function))
		{
			return ($this->db_debug) ? $this->display_error('db_unsupported_function') : FALSE;
		}

		return (func_num_args() > 1)
			? call_user_func_array($function, array_slice(func_get_args(), 1))
			: call_user_func($function);
	}

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

	/**
	 * Set Cache Directory Path
	 *
	 * @param	string	the path to the cache directory
	 * @return	void
	 */
	public function cache_set_path($path = '')
	{
		$this->cachedir = $path;
	}

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

	/**
	 * Enable Query Caching
	 *
	 * @return	bool	cache_on value
	 */
	public function cache_on()
	{
		return $this->cache_on = TRUE;
	}

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

	/**
	 * Disable Query Caching
	 *
	 * @return	bool	cache_on value
	 */
	public function cache_off()
	{
		return $this->cache_on = FALSE;
	}

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

	/**
	 * Delete the cache files associated with a particular URI
	 *
	 * @param	string	$segment_one = ''
	 * @param	string	$segment_two = ''
	 * @return	bool
	 */
	public function cache_delete($segment_one = '', $segment_two = '')
	{
		return $this->_cache_init()
			? $this->CACHE->delete($segment_one, $segment_two)
			: FALSE;
	}

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

	/**
	 * Delete All cache files
	 *
	 * @return	bool
	 */
	public function cache_delete_all()
	{
		return $this->_cache_init()
			? $this->CACHE->delete_all()
			: FALSE;
	}

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

	/**
	 * Initialize the Cache Class
	 *
	 * @return	bool
	 */
	protected function _cache_init()
	{
		if ( ! class_exists('CI_DB_Cache', FALSE))
		{
			require_once(BASEPATH.'database/DB_cache.php');
		}
		elseif (is_object($this->CACHE))
		{
			return TRUE;
		}

		$this->CACHE = new CI_DB_Cache($this); // pass db object to support multiple db connections and returned db objects
		return TRUE;
	}

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

	/**
	 * Close DB Connection
	 *
	 * @return	void
	 */
	public function close()
	{
		if ($this->conn_id)
		{
			$this->_close();
			$this->conn_id = FALSE;

It seems like FALSE of type false is incompatible with the declared type object|resource of property $conn_id.

		}
	}

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

	/**
	 * Close DB Connection
	 *
	 * This method would be overridden by most of the drivers.
	 *
	 * @return	void
	 */
	protected function _close()
	{
		$this->conn_id = FALSE;

It seems like FALSE of type false is incompatible with the declared type object|resource of property $conn_id.

	}

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

	/**
	 * Display an error message
	 *
	 * @param	string	the error message
	 * @param	string	any "swap" values
	 * @param	bool	whether to localize the message
	 * @return	string	sends the application/views/errors/error_db.php template
	 */
	public function display_error($error = '', $swap = '', $native = FALSE)
	{
		$LANG =& load_class('Lang', 'core');
		$LANG->load('db');

		$heading = $LANG->line('db_error_heading');

		if ($native === TRUE)
		{
			$message = (array) $error;
		}
		else
		{
			$message = is_array($error) ? $error : array(str_replace('%s', $swap, $LANG->line($error)));
		}

		// Find the most likely culprit of the error by going through
		// the backtrace until the source file is no longer in the
		// database folder.
		$trace = debug_backtrace();
		foreach ($trace as $call)
		{
			if (isset($call['file'], $call['class']))
			{
				// We'll need this on Windows, as APPPATH and BASEPATH will always use forward slashes
				if (DIRECTORY_SEPARATOR !== '/')
				{
					$call['file'] = str_replace('\\', '/', $call['file']);
				}

				if (strpos($call['file'], BASEPATH.'database') === FALSE && strpos($call['class'], 'Loader') === FALSE)
				{
					// Found it - use a relative path for safety
					$message[] = 'Filename: '.str_replace(array(APPPATH, BASEPATH), '', $call['file']);
					$message[] = 'Line Number: '.$call['line'];
					break;
				}
			}
		}

		$error =& load_class('Exceptions', 'core');
		echo $error->show_error($heading, $message, 'error_db');
		exit(8); // EXIT_DATABASE
	}

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

	/**
	 * Protect Identifiers
	 *
	 * This function is used extensively by the Query Builder class, and by
	 * a couple functions in this class.
	 * It takes a column or table name (optionally with an alias) and inserts
	 * the table prefix onto it. Some logic is necessary in order to deal with
	 * column names that include the path. Consider a query like this:
	 *
	 * SELECT * FROM hostname.database.table.column AS c FROM hostname.database.table
	 *
	 * Or a query with aliasing:
	 *
	 * SELECT m.member_id, m.member_name FROM members AS m
	 *
	 * Since the column name can include up to four segments (host, DB, table, column)
	 * or also have an alias prefix, we need to do a bit of work to figure this out and
	 * insert the table prefix (if it exists) in the proper position, and escape only
	 * the correct identifiers.
	 *
	 * @param	string
	 * @param	bool
	 * @param	mixed
	 * @param	bool
	 * @return	string
	 */
	public function protect_identifiers($item, $prefix_single = FALSE, $protect_identifiers = NULL, $field_exists = TRUE)
	{
		if ( ! is_bool($protect_identifiers))
		{
			$protect_identifiers = $this->_protect_identifiers;
		}

		if (is_array($item))
		{
			$escaped_array = array();
			foreach ($item as $k => $v)
			{
				$escaped_array[$this->protect_identifiers($k)] = $this->protect_identifiers($v, $prefix_single, $protect_identifiers, $field_exists);
			}

			return $escaped_array;
		}

		// This is basically a bug fix for queries that use MAX, MIN, etc.
		// If a parenthesis is found we know that we do not need to
		// escape the data or add a prefix. There's probably a more graceful
		// way to deal with this, but I'm not thinking of it -- Rick
		//
		// Added exception for single quotes as well, we don't want to alter
		// literal strings. -- Narf
		if (strcspn($item, "()'") !== strlen($item))
		{
			return $item;
		}

		// Convert tabs or multiple spaces into single spaces
		$item = preg_replace('/\s+/', ' ', trim($item));

		// If the item has an alias declaration we remove it and set it aside.
		// Note: strripos() is used in order to support spaces in table names
		if ($offset = strripos($item, ' AS '))
		{
			$alias = ($protect_identifiers)
				? substr($item, $offset, 4).$this->escape_identifiers(substr($item, $offset + 4))
				: substr($item, $offset);
			$item = substr($item, 0, $offset);
		}
		elseif ($offset = strrpos($item, ' '))
		{
			$alias = ($protect_identifiers)
				? ' '.$this->escape_identifiers(substr($item, $offset + 1))
				: substr($item, $offset);
			$item = substr($item, 0, $offset);
		}
		else
		{
			$alias = '';
		}

		// Break the string apart if it contains periods, then insert the table prefix
		// in the correct location, assuming the period doesn't indicate that we're dealing
		// with an alias. While we're at it, we will escape the components
		if (strpos($item, '.') !== FALSE)
		{
			$parts = explode('.', $item);

			// Does the first segment of the exploded item match
			// one of the aliases previously identified? If so,
			// we have nothing more to do other than escape the item
			//
			// NOTE: The ! empty() condition prevents this method
			//       from breaking when QB isn't enabled.
			if ( ! empty($this->qb_aliased_tables) && in_array($parts[0], $this->qb_aliased_tables))
			{
				if ($protect_identifiers === TRUE)
				{
					foreach ($parts as $key => $val)
					{
						if ( ! in_array($val, $this->_reserved_identifiers))
						{
							$parts[$key] = $this->escape_identifiers($val);
						}
					}

					$item = implode('.', $parts);
				}

				return $item.$alias;
			}

			// Is there a table prefix defined in the config file? If not, no need to do anything
			if ($this->dbprefix !== '')
			{
				// We now add the table prefix based on some logic.
				// Do we have 4 segments (hostname.database.table.column)?
				// If so, we add the table prefix to the column name in the 3rd segment.
				if (isset($parts[3]))
				{
					$i = 2;
				}
				// Do we have 3 segments (database.table.column)?
				// If so, we add the table prefix to the column name in 2nd position
				elseif (isset($parts[2]))
				{
					$i = 1;
				}
				// Do we have 2 segments (table.column)?
				// If so, we add the table prefix to the column name in 1st segment
				else
				{
					$i = 0;
				}

				// This flag is set when the supplied $item does not contain a field name.
				// This can happen when this function is being called from a JOIN.
				if ($field_exists === FALSE)
				{
					$i++;
				}

				// Verify table prefix and replace if necessary
				if ($this->swap_pre !== '' && strpos($parts[$i], $this->swap_pre) === 0)
				{
					$parts[$i] = preg_replace('/^'.$this->swap_pre.'(\S+?)/', $this->dbprefix.'\\1', $parts[$i]);
				}
				// We only add the table prefix if it does not already exist
				elseif (strpos($parts[$i], $this->dbprefix) !== 0)
				{
					$parts[$i] = $this->dbprefix.$parts[$i];
				}

				// Put the parts back together
				$item = implode('.', $parts);
			}

			if ($protect_identifiers === TRUE)
			{
				$item = $this->escape_identifiers($item);
			}

			return $item.$alias;
		}

		// Is there a table prefix? If not, no need to insert it
		if ($this->dbprefix !== '')
		{
			// Verify table prefix and replace if necessary
			if ($this->swap_pre !== '' && strpos($item, $this->swap_pre) === 0)
			{
				$item = preg_replace('/^'.$this->swap_pre.'(\S+?)/', $this->dbprefix.'\\1', $item);
			}
			// Do we prefix an item with no segments?
			elseif ($prefix_single === TRUE && strpos($item, $this->dbprefix) !== 0)
			{
				$item = $this->dbprefix.$item;
			}
		}

		if ($protect_identifiers === TRUE && ! in_array($item, $this->_reserved_identifiers))
		{
			$item = $this->escape_identifiers($item);
		}

		return $item.$alias;
	}

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

	/**
	 * Dummy method that allows Query Builder class to be disabled
	 * and keep count_all() working.
	 *
	 * @return	void
	 */
	protected function _reset_select()
	{
	}

}