WordPress/wp-includes/wp-db.php

<?php
/**
 * WordPress DB Class
 *
 * Original code from {@link http://php.justinvincent.com Justin Vincent (justin@visunet.ie)}
 *
 * @package WordPress
 * @subpackage Database
 * @since 0.71
 */

/**
 * @since 0.71
 */
define( 'EZSQL_VERSION', 'WP1.25' );

/**
 * @since 0.71
 */
define( 'OBJECT', 'OBJECT', true );

/**
 * @since 2.5.0
 */
define( 'OBJECT_K', 'OBJECT_K' );

/**
 * @since 0.71
 */
define( 'ARRAY_A', 'ARRAY_A' );

/**
 * @since 0.71
 */
define( 'ARRAY_N', 'ARRAY_N' );

/**
 * WordPress Database Access Abstraction Object
 *
 * It is possible to replace this class with your own
 * by setting the $wpdb global variable in wp-content/db.php
 * file to your class. The wpdb class will still be included,
 * so you can extend it or simply use your own.
 *
 * @link http://codex.wordpress.org/Function_Reference/wpdb_Class
 *
 * @package WordPress
 * @subpackage Database
 * @since 0.71
 */
class wpdb {

	/**
	 * Whether to show SQL/DB errors
	 *
	 * @since 0.71
	 * @access private
	 * @var bool
	 */
	var $show_errors = false;

	/**
	 * Whether to suppress errors during the DB bootstrapping.
	 *
	 * @access private
	 * @since 2.5.0
	 * @var bool
	 */
	var $suppress_errors = false;

	/**
	 * The last error during query.
	 *
	 * @since 2.5.0
	 * @var string
	 */
	var $last_error = '';

	/**
	 * Amount of queries made
	 *
	 * @since 1.2.0
	 * @access private
	 * @var int
	 */
	var $num_queries = 0;

	/**
	 * Count of rows returned by previous query
	 *
	 * @since 0.71
	 * @access private
	 * @var int
	 */
	var $num_rows = 0;

	/**
	 * Count of affected rows by previous query
	 *
	 * @since 0.71
	 * @access private
	 * @var int
	 */
	var $rows_affected = 0;

	/**
	 * The ID generated for an AUTO_INCREMENT column by the previous query (usually INSERT).
	 *
	 * @since 0.71
	 * @access public
	 * @var int
	 */
	var $insert_id = 0;

	/**
	 * Last query made
	 *
	 * @since 0.71
	 * @access private
	 * @var array
	 */
	var $last_query;

	/**
	 * Results of the last query made
	 *
	 * @since 0.71
	 * @access private
	 * @var array|null
	 */
	var $last_result;

	/**
	 * MySQL result, which is either a resource or boolean.
	 *
	 * @since 0.71
	 * @access protected
	 * @var mixed
	 */
	protected $result;

	/**
	 * Saved info on the table column
	 *
	 * @since 0.71
	 * @access protected
	 * @var array
	 */
	protected $col_info;

	/**
	 * Saved queries that were executed
	 *
	 * @since 1.5.0
	 * @access private
	 * @var array
	 */
	var $queries;

	/**
	 * The number of times to retry reconnecting before dying.
	 *
	 * @since 3.9.0
	 * @access protected
	 * @see wpdb::check_connection()
	 * @var int
	 */
	protected $reconnect_retries = 5;

	/**
	 * WordPress table prefix
	 *
	 * You can set this to have multiple WordPress installations
	 * in a single database. The second reason is for possible
	 * security precautions.
	 *
	 * @since 2.5.0
	 * @access private
	 * @var string
	 */
	var $prefix = '';

	/**
	 * WordPress base table prefix.
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	 public $base_prefix;

	/**
	 * Whether the database queries are ready to start executing.
	 *
	 * @since 2.3.2
	 * @access private
	 * @var bool
	 */
	var $ready = false;

	/**
	 * {@internal Missing Description}}
	 *
	 * @since 3.0.0
	 * @access public
	 * @var int
	 */
	var $blogid = 0;

	/**
	 * {@internal Missing Description}}
	 *
	 * @since 3.0.0
	 * @access public
	 * @var int
	 */
	var $siteid = 0;

	/**
	 * List of WordPress per-blog tables
	 *
	 * @since 2.5.0
	 * @access private
	 * @see wpdb::tables()
	 * @var array
	 */
	var $tables = array( 'posts', 'comments', 'links', 'options', 'postmeta',
		'terms', 'term_taxonomy', 'term_relationships', 'commentmeta' );

	/**
	 * List of deprecated WordPress tables
	 *
	 * categories, post2cat, and link2cat were deprecated in 2.3.0, db version 5539
	 *
	 * @since 2.9.0
	 * @access private
	 * @see wpdb::tables()
	 * @var array
	 */
	var $old_tables = array( 'categories', 'post2cat', 'link2cat' );

	/**
	 * List of WordPress global tables
	 *
	 * @since 3.0.0
	 * @access private
	 * @see wpdb::tables()
	 * @var array
	 */
	var $global_tables = array( 'users', 'usermeta' );

	/**
	 * List of Multisite global tables
	 *
	 * @since 3.0.0
	 * @access private
	 * @see wpdb::tables()
	 * @var array
	 */
	var $ms_global_tables = array( 'blogs', 'signups', 'site', 'sitemeta',
		'sitecategories', 'registration_log', 'blog_versions' );

	/**
	 * WordPress Comments table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $comments;

	/**
	 * WordPress Comment Metadata table
	 *
	 * @since 2.9.0
	 * @access public
	 * @var string
	 */
	var $commentmeta;

	/**
	 * WordPress Links table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $links;

	/**
	 * WordPress Options table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $options;

	/**
	 * WordPress Post Metadata table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $postmeta;

	/**
	 * WordPress Posts table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $posts;

	/**
	 * WordPress Terms table
	 *
	 * @since 2.3.0
	 * @access public
	 * @var string
	 */
	var $terms;

	/**
	 * WordPress Term Relationships table
	 *
	 * @since 2.3.0
	 * @access public
	 * @var string
	 */
	var $term_relationships;

	/**
	 * WordPress Term Taxonomy table
	 *
	 * @since 2.3.0
	 * @access public
	 * @var string
	 */
	var $term_taxonomy;

	/*
	 * Global and Multisite tables
	 */

	/**
	 * WordPress User Metadata table
	 *
	 * @since 2.3.0
	 * @access public
	 * @var string
	 */
	var $usermeta;

	/**
	 * WordPress Users table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $users;

	/**
	 * Multisite Blogs table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $blogs;

	/**
	 * Multisite Blog Versions table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $blog_versions;

	/**
	 * Multisite Registration Log table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $registration_log;

	/**
	 * Multisite Signups table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $signups;

	/**
	 * Multisite Sites table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $site;

	/**
	 * Multisite Sitewide Terms table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $sitecategories;

	/**
	 * Multisite Site Metadata table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $sitemeta;

	/**
	 * Format specifiers for DB columns. Columns not listed here default to %s. Initialized during WP load.
	 *
	 * Keys are column names, values are format types: 'ID' => '%d'
	 *
	 * @since 2.8.0
	 * @see wpdb::prepare()
	 * @see wpdb::insert()
	 * @see wpdb::update()
	 * @see wpdb::delete()
	 * @see wp_set_wpdb_vars()
	 * @access public
	 * @var array
	 */
	var $field_types = array();

	/**
	 * Database table columns charset
	 *
	 * @since 2.2.0
	 * @access public
	 * @var string
	 */
	var $charset;

	/**
	 * Database table columns collate
	 *
	 * @since 2.2.0
	 * @access public
	 * @var string
	 */
	var $collate;

	/**
	 * Database Username
	 *
	 * @since 2.9.0
	 * @access protected
	 * @var string
	 */
	protected $dbuser;

	/**
	 * Database Password
	 *
	 * @since 3.1.0
	 * @access protected
	 * @var string
	 */
	protected $dbpassword;

	/**
	 * Database Name
	 *
	 * @since 3.1.0
	 * @access protected
	 * @var string
	 */
	protected $dbname;

	/**
	 * Database Host
	 *
	 * @since 3.1.0
	 * @access protected
	 * @var string
	 */
	protected $dbhost;

	/**
	 * Database Handle
	 *
	 * @since 0.71
	 * @access protected
	 * @var string
	 */
	protected $dbh;

	/**
	 * A textual description of the last query/get_row/get_var call
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $func_call;

	/**
	 * Whether MySQL is used as the database engine.
	 *
	 * Set in WPDB::db_connect() to true, by default. This is used when checking
	 * against the required MySQL version for WordPress. Normally, a replacement
	 * database drop-in (db.php) will skip these checks, but setting this to true
	 * will force the checks to occur.
	 *
	 * @since 3.3.0
	 * @access public
	 * @var bool
	 */
	public $is_mysql = null;

	/**
	 * A list of incompatible SQL modes.
	 *
	 * @since 3.9.0
	 * @access protected
	 * @var array
	 */
	protected $incompatible_modes = array( 'NO_ZERO_DATE', 'ONLY_FULL_GROUP_BY',
		'STRICT_TRANS_TABLES', 'STRICT_ALL_TABLES', 'TRADITIONAL' );

	/**
	 * Whether to use mysqli over mysql.
	 *
	 * @since 3.9.0
	 * @access private
	 * @var bool
	 */
	private $use_mysqli = false;

	/**
	 * Connects to the database server and selects a database
	 *
	 * PHP5 style constructor for compatibility with PHP5. Does
	 * the actual setting up of the class properties and connection
	 * to the database.
	 *
	 * @link http://core.trac.wordpress.org/ticket/3354
	 * @since 2.0.8
	 *
	 * @param string $dbuser MySQL database user
	 * @param string $dbpassword MySQL database password
	 * @param string $dbname MySQL database name
	 * @param string $dbhost MySQL database host
	 */
	function __construct( $dbuser, $dbpassword, $dbname, $dbhost ) {
		register_shutdown_function( array( $this, '__destruct' ) );

		if ( WP_DEBUG && WP_DEBUG_DISPLAY )
			$this->show_errors();

		$this->use_mysqli = ( version_compare( phpversion(), '5.5', '>=' ) && function_exists( 'mysqli_connect' ) );

		$this->init_charset();

		$this->dbuser = $dbuser;
		$this->dbpassword = $dbpassword;
		$this->dbname = $dbname;
		$this->dbhost = $dbhost;

		$this->db_connect();
	}

	/**
	 * PHP5 style destructor and will run when database object is destroyed.
	 *
	 * @see wpdb::__construct()
	 * @since 2.0.8
	 * @return bool true
	 */
	function __destruct() {
		return true;
	}

	/**
	 * PHP5 style magic getter, used to lazy-load expensive data.
	 *
	 * @since 3.5.0
	 *
	 * @param string $name The private member to get, and optionally process
	 * @return mixed The private member
	 */
	function __get( $name ) {
		if ( 'col_info' == $name )
			$this->load_col_info();

		return $this->$name;
	}

	/**
	 * Magic function, for backwards compatibility
	 *
	 * @since 3.5.0
	 *
	 * @param string $name  The private member to set
	 * @param mixed  $value The value to set
	 */
	function __set( $name, $value ) {
		$this->$name = $value;
	}

	/**
	 * Magic function, for backwards compatibility
	 *
	 * @since 3.5.0
	 *
	 * @param string $name  The private member to check
	 *
	 * @return bool If the member is set or not
	 */
	function __isset( $name ) {
		return isset( $this->$name );
	}

	/**
	 * Magic function, for backwards compatibility
	 *
	 * @since 3.5.0
	 *
	 * @param string $name  The private member to unset
	 */
	function __unset( $name ) {
		unset( $this->$name );
	}

	/**
	 * Set $this->charset and $this->collate
	 *
	 * @since 3.1.0
	 */
	function init_charset() {
		if ( function_exists('is_multisite') && is_multisite() ) {
			$this->charset = 'utf8';
			if ( defined( 'DB_COLLATE' ) && DB_COLLATE )
				$this->collate = DB_COLLATE;
			else
				$this->collate = 'utf8_general_ci';
		} elseif ( defined( 'DB_COLLATE' ) ) {
			$this->collate = DB_COLLATE;
		}

		if ( defined( 'DB_CHARSET' ) )
			$this->charset = DB_CHARSET;
	}

	/**
	 * Sets the connection's character set.
	 *
	 * @since 3.1.0
	 *
	 * @param resource $dbh     The resource given by mysql_connect
	 * @param string   $charset The character set (optional)
	 * @param string   $collate The collation (optional)
	 */
	function set_charset( $dbh, $charset = null, $collate = null ) {
		if ( ! isset( $charset ) )
			$charset = $this->charset;
		if ( ! isset( $collate ) )
			$collate = $this->collate;
		if ( $this->has_cap( 'collation' ) && ! empty( $charset ) ) {
			if ( $this->use_mysqli ) {
				if ( function_exists( 'mysqli_set_charset' ) && $this->has_cap( 'set_charset' ) ) {
					mysqli_set_charset( $dbh, $charset );
				} else {
					$query = $this->prepare( 'SET NAMES %s', $charset );
					if ( ! empty( $collate ) )
						$query .= $this->prepare( ' COLLATE %s', $collate );
					mysqli_query( $query, $dbh );
				}
			} else {
				if ( function_exists( 'mysql_set_charset' ) && $this->has_cap( 'set_charset' ) ) {
					mysql_set_charset( $charset, $dbh );
				} else {
					$query = $this->prepare( 'SET NAMES %s', $charset );
					if ( ! empty( $collate ) )
						$query .= $this->prepare( ' COLLATE %s', $collate );
					mysql_query( $query, $dbh );
				}
			}
		}
	}

	/**
	 * Change the current SQL mode, and ensure its WordPress compatibility.
	 *
	 * If no modes are passed, it will ensure the current MySQL server
	 * modes are compatible.
	 *
	 * @since 3.9.0
	 *
	 * @param array $modes Optional. A list of SQL modes to set.
	 */
	function set_sql_mode( $modes = array() ) {
		if ( empty( $modes ) ) {
			if ( $this->use_mysqli ) {
				$res = mysqli_query( $this->dbh, 'SELECT @@SESSION.sql_mode' );
			} else {
				$res = mysql_query( 'SELECT @@SESSION.sql_mode', $this->dbh );
			}

			if ( empty( $res ) ) {
				return;
			}

			if ( $this->use_mysqli ) {
				$modes_array = mysqli_fetch_array( $res );
				if ( empty( $modes_array[0] ) ) {
					return;
				}
				$modes_str = $modes_array[0];
			} else {
				$modes_str = mysql_result( $res, 0 );
			}

			if ( empty( $modes_str ) ) {
				return;
			}

			$modes = explode( ',', $modes_str );
		}

		$modes = array_change_key_case( $modes, CASE_UPPER );

		/**
		 * Filter the list of incompatible SQL modes to exclude.
		 *
		 * @since 3.9.0
		 *
		 * @see wpdb::$incompatible_modes
		 *
		 * @param array $incompatible_modes An array of incompatible modes.
		 */
		$incompatible_modes = (array) apply_filters( 'incompatible_sql_modes', $this->incompatible_modes );

		foreach( $modes as $i => $mode ) {
			if ( in_array( $mode, $incompatible_modes ) ) {
				unset( $modes[ $i ] );
			}
		}

		$modes_str = implode( ',', $modes );

		if ( $this->use_mysqli ) {
			mysqli_query( $this->dbh, "SET SESSION sql_mode='$modes_str'" );
		} else {
			mysql_query( "SET SESSION sql_mode='$modes_str'", $this->dbh );
		}
	}

	/**
	 * Sets the table prefix for the WordPress tables.
	 *
	 * @since 2.5.0
	 *
	 * @param string $prefix Alphanumeric name for the new prefix.
	 * @param bool $set_table_names Optional. Whether the table names, e.g. wpdb::$posts, should be updated or not.
	 * @return string|WP_Error Old prefix or WP_Error on error
	 */
	function set_prefix( $prefix, $set_table_names = true ) {

		if ( preg_match( '|[^a-z0-9_]|i', $prefix ) )
			return new WP_Error('invalid_db_prefix', 'Invalid database prefix' );

		$old_prefix = is_multisite() ? '' : $prefix;

		if ( isset( $this->base_prefix ) )
			$old_prefix = $this->base_prefix;

		$this->base_prefix = $prefix;

		if ( $set_table_names ) {
			foreach ( $this->tables( 'global' ) as $table => $prefixed_table )
				$this->$table = $prefixed_table;

			if ( is_multisite() && empty( $this->blogid ) )
				return $old_prefix;

			$this->prefix = $this->get_blog_prefix();

			foreach ( $this->tables( 'blog' ) as $table => $prefixed_table )
				$this->$table = $prefixed_table;

			foreach ( $this->tables( 'old' ) as $table => $prefixed_table )
				$this->$table = $prefixed_table;
		}
		return $old_prefix;
	}

	/**
	 * Sets blog id.
	 *
	 * @since 3.0.0
	 * @access public
	 * @param int $blog_id
	 * @param int $site_id Optional.
	 * @return string previous blog id
	 */
	function set_blog_id( $blog_id, $site_id = 0 ) {
		if ( ! empty( $site_id ) )
			$this->siteid = $site_id;

		$old_blog_id  = $this->blogid;
		$this->blogid = $blog_id;

		$this->prefix = $this->get_blog_prefix();

		foreach ( $this->tables( 'blog' ) as $table => $prefixed_table )
			$this->$table = $prefixed_table;

		foreach ( $this->tables( 'old' ) as $table => $prefixed_table )
			$this->$table = $prefixed_table;

		return $old_blog_id;
	}

	/**
	 * Gets blog prefix.
	 *
	 * @uses is_multisite()
	 * @since 3.0.0
	 * @param int $blog_id Optional.
	 * @return string Blog prefix.
	 */
	function get_blog_prefix( $blog_id = null ) {
		if ( is_multisite() ) {
			if ( null === $blog_id )
				$blog_id = $this->blogid;
			$blog_id = (int) $blog_id;
			if ( defined( 'MULTISITE' ) && ( 0 == $blog_id || 1 == $blog_id ) )
				return $this->base_prefix;
			else
				return $this->base_prefix . $blog_id . '_';
		} else {
			return $this->base_prefix;
		}
	}

	/**
	 * Returns an array of WordPress tables.
	 *
	 * Also allows for the CUSTOM_USER_TABLE and CUSTOM_USER_META_TABLE to
	 * override the WordPress users and usermeta tables that would otherwise
	 * be determined by the prefix.
	 *
	 * The scope argument can take one of the following:
	 *
	 * 'all' - returns 'all' and 'global' tables. No old tables are returned.
	 * 'blog' - returns the blog-level tables for the queried blog.
	 * 'global' - returns the global tables for the installation, returning multisite tables only if running multisite.
	 * 'ms_global' - returns the multisite global tables, regardless if current installation is multisite.
	 * 'old' - returns tables which are deprecated.
	 *
	 * @since 3.0.0
	 * @uses wpdb::$tables
	 * @uses wpdb::$old_tables
	 * @uses wpdb::$global_tables
	 * @uses wpdb::$ms_global_tables
	 * @uses is_multisite()
	 *
	 * @param string $scope Optional. Can be all, global, ms_global, blog, or old tables. Defaults to all.
	 * @param bool $prefix Optional. Whether to include table prefixes. Default true. If blog
	 * 	prefix is requested, then the custom users and usermeta tables will be mapped.
	 * @param int $blog_id Optional. The blog_id to prefix. Defaults to wpdb::$blogid. Used only when prefix is requested.
	 * @return array Table names. When a prefix is requested, the key is the unprefixed table name.
	 */
	function tables( $scope = 'all', $prefix = true, $blog_id = 0 ) {
		switch ( $scope ) {
			case 'all' :
				$tables = array_merge( $this->global_tables, $this->tables );
				if ( is_multisite() )
					$tables = array_merge( $tables, $this->ms_global_tables );
				break;
			case 'blog' :
				$tables = $this->tables;
				break;
			case 'global' :
				$tables = $this->global_tables;
				if ( is_multisite() )
					$tables = array_merge( $tables, $this->ms_global_tables );
				break;
			case 'ms_global' :
				$tables = $this->ms_global_tables;
				break;
			case 'old' :
				$tables = $this->old_tables;
				break;
			default :
				return array();
				break;
		}

		if ( $prefix ) {
			if ( ! $blog_id )
				$blog_id = $this->blogid;
			$blog_prefix = $this->get_blog_prefix( $blog_id );
			$base_prefix = $this->base_prefix;
			$global_tables = array_merge( $this->global_tables, $this->ms_global_tables );
			foreach ( $tables as $k => $table ) {
				if ( in_array( $table, $global_tables ) )
					$tables[ $table ] = $base_prefix . $table;
				else
					$tables[ $table ] = $blog_prefix . $table;
				unset( $tables[ $k ] );
			}

			if ( isset( $tables['users'] ) && defined( 'CUSTOM_USER_TABLE' ) )
				$tables['users'] = CUSTOM_USER_TABLE;

			if ( isset( $tables['usermeta'] ) && defined( 'CUSTOM_USER_META_TABLE' ) )
				$tables['usermeta'] = CUSTOM_USER_META_TABLE;
		}

		return $tables;
	}

	/**
	 * Selects a database using the current database connection.
	 *
	 * The database name will be changed based on the current database
	 * connection. On failure, the execution will bail and display an DB error.
	 *
	 * @since 0.71
	 *
	 * @param string $db MySQL database name
	 * @param resource $dbh Optional link identifier.
	 * @return null Always null.
	 */
	function select( $db, $dbh = null ) {
		if ( is_null($dbh) )
			$dbh = $this->dbh;

		if ( $this->use_mysqli ) {
			$success = @mysqli_select_db( $dbh, $db );
		} else {
			$success = @mysql_select_db( $db, $dbh );
		}
		if ( ! $success ) {
			$this->ready = false;
			wp_load_translations_early();
			$this->bail( sprintf( __( '<h1>Can&#8217;t select database</h1>
<p>We were able to connect to the database server (which means your username and password is okay) but not able to select the <code>%1$s</code> database.</p>
<ul>
<li>Are you sure it exists?</li>
<li>Does the user <code>%2$s</code> have permission to use the <code>%1$s</code> database?</li>
<li>On some systems the name of your database is prefixed with your username, so it would be like <code>username_%1$s</code>. Could that be the problem?</li>
</ul>
<p>If you don\'t know how to set up a database you should <strong>contact your host</strong>. If all else fails you may find help at the <a href="http://wordpress.org/support/">WordPress Support Forums</a>.</p>' ), htmlspecialchars( $db, ENT_QUOTES ), htmlspecialchars( $this->dbuser, ENT_QUOTES ) ), 'db_select_fail' );
			return;
		}
	}

	/**
	 * Do not use, deprecated.
	 *
	 * Use esc_sql() or wpdb::prepare() instead.
	 *
	 * @since 2.8.0
	 * @deprecated 3.6.0
	 * @see wpdb::prepare
	 * @see esc_sql()
	 * @access private
	 *
	 * @param string $string
	 * @return string
	 */
	function _weak_escape( $string ) {
		if ( func_num_args() === 1 && function_exists( '_deprecated_function' ) )
			_deprecated_function( __METHOD__, '3.6', 'wpdb::prepare() or esc_sql()' );
		return addslashes( $string );
	}

	/**
	 * Real escape, using mysqli_real_escape_string() or mysql_real_escape_string()
	 *
	 * @see mysqli_real_escape_string()
	 * @see mysql_real_escape_string()
	 * @since 2.8.0
	 * @access private
	 *
	 * @param  string $string to escape
	 * @return string escaped
	 */
	function _real_escape( $string ) {
		if ( $this->dbh ) {
			if ( $this->use_mysqli ) {
				return mysqli_real_escape_string( $this->dbh, $string );
			} else {
				return mysql_real_escape_string( $string, $this->dbh );
			}
		}

		$class = get_class( $this );
		_doing_it_wrong( $class, "$class must set a database connection for use with escaping.", E_USER_NOTICE );
		return addslashes( $string );
	}

	/**
	 * Escape data. Works on arrays.
	 *
	 * @uses wpdb::_real_escape()
	 * @since  2.8.0
	 * @access private
	 *
	 * @param  string|array $data
	 * @return string|array escaped
	 */
	function _escape( $data ) {
		if ( is_array( $data ) ) {
			foreach ( $data as $k => $v ) {
				if ( is_array($v) )
					$data[$k] = $this->_escape( $v );
				else
					$data[$k] = $this->_real_escape( $v );
			}
		} else {
			$data = $this->_real_escape( $data );
		}

		return $data;
	}

	/**
	 * Do not use, deprecated.
	 *
	 * Use esc_sql() or wpdb::prepare() instead.
	 *
	 * @since 0.71
	 * @deprecated 3.6.0
	 * @see wpdb::prepare()
	 * @see esc_sql()
	 *
	 * @param mixed $data
	 * @return mixed
	 */
	function escape( $data ) {
		if ( func_num_args() === 1 && function_exists( '_deprecated_function' ) )
			_deprecated_function( __METHOD__, '3.6', 'wpdb::prepare() or esc_sql()' );
		if ( is_array( $data ) ) {
			foreach ( $data as $k => $v ) {
				if ( is_array( $v ) )
					$data[$k] = $this->escape( $v, 'recursive' );
				else
					$data[$k] = $this->_weak_escape( $v, 'internal' );
			}
		} else {
			$data = $this->_weak_escape( $data, 'internal' );
		}

		return $data;
	}

	/**
	 * Escapes content by reference for insertion into the database, for security
	 *
	 * @uses wpdb::_real_escape()
	 * @since 2.3.0
	 * @param string $string to escape
	 * @return void
	 */
	function escape_by_ref( &$string ) {
		if ( ! is_float( $string ) )
			$string = $this->_real_escape( $string );
	}

	/**
	 * Prepares a SQL query for safe execution. Uses sprintf()-like syntax.
	 *
	 * The following directives can be used in the query format string:
	 *   %d (integer)
	 *   %f (float)
	 *   %s (string)
	 *   %% (literal percentage sign - no argument needed)
	 *
	 * All of %d, %f, and %s are to be left unquoted in the query string and they need an argument passed for them.
	 * Literals (%) as parts of the query must be properly written as %%.
	 *
	 * This function only supports a small subset of the sprintf syntax; it only supports %d (integer), %f (float), and %s (string).
	 * Does not support sign, padding, alignment, width or precision specifiers.
	 * Does not support argument numbering/swapping.
	 *
	 * May be called like {@link http://php.net/sprintf sprintf()} or like {@link http://php.net/vsprintf vsprintf()}.
	 *
	 * Both %d and %s should be left unquoted in the query string.
	 *
	 * <code>
	 * wpdb::prepare( "SELECT * FROM `table` WHERE `column` = %s AND `field` = %d", 'foo', 1337 )
	 * wpdb::prepare( "SELECT DATE_FORMAT(`field`, '%%c') FROM `table` WHERE `column` = %s", 'foo' );
	 * </code>
	 *
	 * @link http://php.net/sprintf Description of syntax.
	 * @since 2.3.0
	 *
	 * @param string $query Query statement with sprintf()-like placeholders
	 * @param array|mixed $args The array of variables to substitute into the query's placeholders if being called like
	 * 	{@link http://php.net/vsprintf vsprintf()}, or the first variable to substitute into the query's placeholders if
	 * 	being called like {@link http://php.net/sprintf sprintf()}.
	 * @param mixed $args,... further variables to substitute into the query's placeholders if being called like
	 * 	{@link http://php.net/sprintf sprintf()}.
	 * @return null|false|string Sanitized query string, null if there is no query, false if there is an error and string
	 * 	if there was something to prepare
	 */
	function prepare( $query, $args ) {
		if ( is_null( $query ) )
			return;

		// This is not meant to be foolproof -- but it will catch obviously incorrect usage.
		if ( strpos( $query, '%' ) === false ) {
			_doing_it_wrong( 'wpdb::prepare', sprintf( __( 'The query argument of %s must have a placeholder.' ), 'wpdb::prepare()' ), '3.9' );
		}

		$args = func_get_args();
		array_shift( $args );
		// If args were passed as an array (as in vsprintf), move them up
		if ( isset( $args[0] ) && is_array($args[0]) )
			$args = $args[0];
		$query = str_replace( "'%s'", '%s', $query ); // in case someone mistakenly already singlequoted it
		$query = str_replace( '"%s"', '%s', $query ); // doublequote unquoting
		$query = preg_replace( '|(?<!%)%f|' , '%F', $query ); // Force floats to be locale unaware
		$query = preg_replace( '|(?<!%)%s|', "'%s'", $query ); // quote the strings, avoiding escaped strings like %%s
		array_walk( $args, array( $this, 'escape_by_ref' ) );
		return @vsprintf( $query, $args );
	}

	/**
	 * Print SQL/DB error.
	 *
	 * @since 0.71
	 * @global array $EZSQL_ERROR Stores error information of query and error string
	 *
	 * @param string $str The error to display
	 * @return bool False if the showing of errors is disabled.
	 */
	function print_error( $str = '' ) {
		global $EZSQL_ERROR;

		if ( !$str ) {
			if ( $this->use_mysqli ) {
				$str = mysqli_error( $this->dbh );
			} else {
				$str = mysql_error( $this->dbh );
			}
		}
		$EZSQL_ERROR[] = array( 'query' => $this->last_query, 'error_str' => $str );

		if ( $this->suppress_errors )
			return false;

		wp_load_translations_early();

		if ( $caller = $this->get_caller() )
			$error_str = sprintf( __( 'WordPress database error %1$s for query %2$s made by %3$s' ), $str, $this->last_query, $caller );
		else
			$error_str = sprintf( __( 'WordPress database error %1$s for query %2$s' ), $str, $this->last_query );

		error_log( $error_str );

		// Are we showing errors?
		if ( ! $this->show_errors )
			return false;

		// If there is an error then take note of it
		if ( is_multisite() ) {
			$msg = "WordPress database error: [$str]\n{$this->last_query}\n";
			if ( defined( 'ERRORLOGFILE' ) )
				error_log( $msg, 3, ERRORLOGFILE );
			if ( defined( 'DIEONDBERROR' ) )
				wp_die( $msg );
		} else {
			$str   = htmlspecialchars( $str, ENT_QUOTES );
			$query = htmlspecialchars( $this->last_query, ENT_QUOTES );

			print "<div id='error'>
			<p class='wpdberror'><strong>WordPress database error:</strong> [$str]<br />
			<code>$query</code></p>
			</div>";
		}
	}

	/**
	 * Enables showing of database errors.
	 *
	 * This function should be used only to enable showing of errors.
	 * wpdb::hide_errors() should be used instead for hiding of errors. However,
	 * this function can be used to enable and disable showing of database
	 * errors.
	 *
	 * @since 0.71
	 * @see wpdb::hide_errors()
	 *
	 * @param bool $show Whether to show or hide errors
	 * @return bool Old value for showing errors.
	 */
	function show_errors( $show = true ) {
		$errors = $this->show_errors;
		$this->show_errors = $show;
		return $errors;
	}

	/**
	 * Disables showing of database errors.
	 *
	 * By default database errors are not shown.
	 *
	 * @since 0.71
	 * @see wpdb::show_errors()
	 *
	 * @return bool Whether showing of errors was active
	 */
	function hide_errors() {
		$show = $this->show_errors;
		$this->show_errors = false;
		return $show;
	}

	/**
	 * Whether to suppress database errors.
	 *
	 * By default database errors are suppressed, with a simple
	 * call to this function they can be enabled.
	 *
	 * @since 2.5.0
	 * @see wpdb::hide_errors()
	 * @param bool $suppress Optional. New value. Defaults to true.
	 * @return bool Old value
	 */
	function suppress_errors( $suppress = true ) {
		$errors = $this->suppress_errors;
		$this->suppress_errors = (bool) $suppress;
		return $errors;
	}

	/**
	 * Kill cached query results.
	 *
	 * @since 0.71
	 * @return void
	 */
	function flush() {
		$this->last_result = array();
		$this->col_info    = null;
		$this->last_query  = null;
		$this->rows_affected = $this->num_rows = 0;
		$this->last_error  = '';

		if ( is_resource( $this->result ) ) {
			if ( $this->use_mysqli ) {
				mysqli_free_result( $this->result );
			} else {
				mysql_free_result( $this->result );
			}
		}
	}

	/**
	 * Connect to and select database.
	 *
	 * @since 3.0.0
	 *
	 * @param bool $allow_bail Optional. Allows the function to bail, default true. If this is set
	 *                         to false, you will need to handle the lack of database connection
	 *                         manually. Available since 3.9.0.
	 *
	 * @return bool True with a successful connection, false on failure.
	 */
	function db_connect( $allow_bail = true ) {

		$this->is_mysql = true;

		$new_link = defined( 'MYSQL_NEW_LINK' ) ? MYSQL_NEW_LINK : true;
		$client_flags = defined( 'MYSQL_CLIENT_FLAGS' ) ? MYSQL_CLIENT_FLAGS : 0;

		if ( $this->use_mysqli ) {
			$this->dbh = mysqli_init();

			// mysqli_real_connect doesn't support the host param including a port or socket
			// like mysql_connect does. This duplicates how mysql_connect detects a port and/or socket file.
			$port = null;
			$socket = null;
			$host = $this->dbhost;
			$port_or_socket = strstr( $host, ':' );
			if ( ! empty( $port_or_socket ) ) {
				$host = strstr( $host, ':', true );
				$port_or_socket = substr( $port_or_socket, 1 );
				if ( 0 !== strpos( $port_or_socket, '/' ) ) {
					$port = intval( $port_or_socket );
					$maybe_socket = strstr( $port_or_socket, ':' );
					if ( ! empty( $maybe_socket ) ) {
						$socket = substr( $maybe_socket, 1 );
					}
				} else {
					$socket = $port_or_socket;
				}
			}

			if ( WP_DEBUG ) {
				mysqli_real_connect( $this->dbh, $host, $this->dbuser, $this->dbpassword, null, $port, $socket, $client_flags );
			} else {
				@mysqli_real_connect( $this->dbh, $host, $this->dbuser, $this->dbpassword, null, $port, $socket, $client_flags );
			}
		} else {
			if ( WP_DEBUG ) {
				$this->dbh = mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags );
			} else {
				$this->dbh = @mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags );
			}
		}

		if ( ! $this->dbh && $allow_bail ) {
			wp_load_translations_early();

			// Load custom DB error template, if present.
			if ( file_exists( WP_CONTENT_DIR . '/db-error.php' ) ) {
				require_once( WP_CONTENT_DIR . '/db-error.php' );
				die();
			}

			$this->bail( sprintf( __( "
<h1>Error establishing a database connection</h1>
<p>This either means that the username and password information in your <code>wp-config.php</code> file is incorrect or we can't contact the database server at <code>%s</code>. This could mean your host's database server is down.</p>
<ul>
	<li>Are you sure you have the correct username and password?</li>
	<li>Are you sure that you have typed the correct hostname?</li>
	<li>Are you sure that the database server is running?</li>
</ul>
<p>If you're unsure what these terms mean you should probably contact your host. If you still need help you can always visit the <a href='http://wordpress.org/support/'>WordPress Support Forums</a>.</p>
" ), htmlspecialchars( $this->dbhost, ENT_QUOTES ) ), 'db_connect_fail' );

			return false;
		} else if ( $this->dbh ) {
			$this->set_charset( $this->dbh );
			$this->set_sql_mode();
			$this->ready = true;
			$this->select( $this->dbname, $this->dbh );

			return true;
		}

		return false;
	}

	/**
	 * Check that the connection to the database is still up. If not, try to reconnect.
	 *
	 * If this function is unable to reconnect, it will forcibly die.
	 *
	 * @since 3.9.0
	 *
	 * @return bool True if the connection is up.
	 */
	function check_connection() {
		if ( $this->use_mysqli ) {
			if ( @mysqli_ping( $this->dbh ) ) {
				return true;
			}
		} else {
			if ( @mysql_ping( $this->dbh ) ) {
				return true;
			}
		}

		$error_reporting = false;

		// Disable warnings, as we don't want to see a multitude of "unable to connect" messages
		if ( WP_DEBUG ) {
			$error_reporting = error_reporting();
			error_reporting( $error_reporting & ~E_WARNING );
		}

		for ( $tries = 1; $tries <= $this->reconnect_retries; $tries++ ) {
			// On the last try, re-enable warnings. We want to see a single instance of the
			// "unable to connect" message on the bail() screen, if it appears.
			if ( $this->reconnect_retries === $tries && WP_DEBUG ) {
				error_reporting( $error_reporting );
			}

			if ( $this->db_connect( false ) ) {
				if ( $error_reporting ) {
					error_reporting( $error_reporting );
				}

				return true;
			}

			sleep( 1 );
		}

		// We weren't able to reconnect, so we better bail.
		$this->bail( sprintf( ( "
<h1>Error reconnecting to the database</h1>
<p>This means that we lost contact with the database server at <code>%s</code>. This could mean your host's database server is down.</p>
<ul>
	<li>Are you sure that the database server is running?</li>
	<li>Are you sure that the database server is not under particularly heavy load?</li>
</ul>
<p>If you're unsure what these terms mean you should probably contact your host. If you still need help you can always visit the <a href='http://wordpress.org/support/'>WordPress Support Forums</a>.</p>
" ), htmlspecialchars( $this->dbhost, ENT_QUOTES ) ), 'db_connect_fail' );

		// Call dead_db() if bail didn't die, because this database is no more. It has ceased to be (at least temporarily).
		dead_db();
	}

	/**
	 * Perform a MySQL database query, using current database connection.
	 *
	 * More information can be found on the codex page.
	 *
	 * @since 0.71
	 *
	 * @param string $query Database query
	 * @return int|false Number of rows affected/selected or false on error
	 */
	function query( $query ) {
		if ( ! $this->ready )
			return false;

		/**
		 * Filter the database query.
		 *
		 * Some queries are made before the plugins have been loaded,
		 * and thus cannot be filtered with this method.
		 *
		 * @since 2.1.0
		 *
		 * @param string $query Database query.
		 */
		$query = apply_filters( 'query', $query );

		$return_val = 0;
		$this->flush();

		// Log how the function was called
		$this->func_call = "\$db->query(\"$query\")";

		// Keep track of the last query for debug..
		$this->last_query = $query;

		$this->_do_query( $query );

		// MySQL server has gone away, try to reconnect
		$mysql_errno = 0;
		if ( ! empty( $this->dbh ) ) {
			if ( $this->use_mysqli ) {
				$mysql_errno = mysqli_errno( $this->dbh );
			} else {
				$mysql_errno = mysql_errno( $this->dbh );
			}
		}

		if ( empty( $this->dbh ) || 2006 == $mysql_errno ) {
			if ( $this->check_connection() ) {
				$this->_do_query( $query );
			}
		}

		// If there is an error then take note of it..
		if ( $this->use_mysqli ) {
			$this->last_error = mysqli_error( $this->dbh );
		} else {
			$this->last_error = mysql_error( $this->dbh );
		}

		if ( $this->last_error ) {
			// Clear insert_id on a subsequent failed insert.
			if ( $this->insert_id && preg_match( '/^\s*(insert|replace)\s/i', $query ) )
				$this->insert_id = 0;

			$this->print_error();
			return false;
		}

		if ( preg_match( '/^\s*(create|alter|truncate|drop)\s/i', $query ) ) {
			$return_val = $this->result;
		} elseif ( preg_match( '/^\s*(insert|delete|update|replace)\s/i', $query ) ) {
			if ( $this->use_mysqli ) {
				$this->rows_affected = mysqli_affected_rows( $this->dbh );
			} else {
				$this->rows_affected = mysql_affected_rows( $this->dbh );
			}
			// Take note of the insert_id
			if ( preg_match( '/^\s*(insert|replace)\s/i', $query ) ) {
				if ( $this->use_mysqli ) {
					$this->insert_id = mysqli_insert_id( $this->dbh );
				} else {
					$this->insert_id = mysql_insert_id( $this->dbh );
				}
			}
			// Return number of rows affected
			$return_val = $this->rows_affected;
		} else {
			$num_rows = 0;
			if ( $this->use_mysqli ) {
				while ( $row = @mysqli_fetch_object( $this->result ) ) {
					$this->last_result[$num_rows] = $row;
					$num_rows++;
				}
			} else {
				while ( $row = @mysql_fetch_object( $this->result ) ) {
					$this->last_result[$num_rows] = $row;
					$num_rows++;
				}
			}

			// Log number of rows the query returned
			// and return number of rows selected
			$this->num_rows = $num_rows;
			$return_val     = $num_rows;
		}

		return $return_val;
	}

	/**
	 * Internal function to perform the mysql_query call
	 *
	 * @since 3.9.0
	 *
	 * @access private
	 * @see wpdb::query()
	 *
	 * @param string $query The query to run
	 */
	private function _do_query( $query ) {
		if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES ) {
			$this->timer_start();
		}

		if ( $this->use_mysqli ) {
			$this->result = @mysqli_query( $this->dbh, $query );
		} else {
			$this->result = @mysql_query( $query, $this->dbh );
		}
		$this->num_queries++;

		if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES ) {
			$this->queries[] = array( $query, $this->timer_stop(), $this->get_caller() );
		}
	}

	/**
	 * Insert a row into a table.
	 *
	 * <code>
	 * wpdb::insert( 'table', array( 'column' => 'foo', 'field' => 'bar' ) )
	 * wpdb::insert( 'table', array( 'column' => 'foo', 'field' => 1337 ), array( '%s', '%d' ) )
	 * </code>
	 *
	 * @since 2.5.0
	 * @see wpdb::prepare()
	 * @see wpdb::$field_types
	 * @see wp_set_wpdb_vars()
	 *
	 * @param string $table table name
	 * @param array $data Data to insert (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data. If string, that format will be used for all of the values in $data.
	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
	 * @return int|false The number of rows inserted, or false on error.
	 */
	function insert( $table, $data, $format = null ) {
		return $this->_insert_replace_helper( $table, $data, $format, 'INSERT' );
	}

	/**
	 * Replace a row into a table.
	 *
	 * <code>
	 * wpdb::replace( 'table', array( 'column' => 'foo', 'field' => 'bar' ) )
	 * wpdb::replace( 'table', array( 'column' => 'foo', 'field' => 1337 ), array( '%s', '%d' ) )
	 * </code>
	 *
	 * @since 3.0.0
	 * @see wpdb::prepare()
	 * @see wpdb::$field_types
	 * @see wp_set_wpdb_vars()
	 *
	 * @param string $table table name
	 * @param array $data Data to insert (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data. If string, that format will be used for all of the values in $data.
	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
	 * @return int|false The number of rows affected, or false on error.
	 */
	function replace( $table, $data, $format = null ) {
		return $this->_insert_replace_helper( $table, $data, $format, 'REPLACE' );
	}

	/**
	 * Helper function for insert and replace.
	 *
	 * Runs an insert or replace query based on $type argument.
	 *
	 * @access private
	 * @since 3.0.0
	 * @see wpdb::prepare()
	 * @see wpdb::$field_types
	 * @see wp_set_wpdb_vars()
	 *
	 * @param string $table table name
	 * @param array $data Data to insert (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data. If string, that format will be used for all of the values in $data.
	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
	 * @param string $type Optional. What type of operation is this? INSERT or REPLACE. Defaults to INSERT.
	 * @return int|false The number of rows affected, or false on error.
	 */
	function _insert_replace_helper( $table, $data, $format = null, $type = 'INSERT' ) {
		if ( ! in_array( strtoupper( $type ), array( 'REPLACE', 'INSERT' ) ) )
			return false;
		$this->insert_id = 0;
		$formats = $format = (array) $format;
		$fields = array_keys( $data );
		$formatted_fields = array();
		foreach ( $fields as $field ) {
			if ( !empty( $format ) )
				$form = ( $form = array_shift( $formats ) ) ? $form : $format[0];
			elseif ( isset( $this->field_types[$field] ) )
				$form = $this->field_types[$field];
			else
				$form = '%s';
			$formatted_fields[] = $form;
		}
		$sql = "{$type} INTO `$table` (`" . implode( '`,`', $fields ) . "`) VALUES (" . implode( ",", $formatted_fields ) . ")";
		return $this->query( $this->prepare( $sql, $data ) );
	}

	/**
	 * Update a row in the table
	 *
	 * <code>
	 * wpdb::update( 'table', array( 'column' => 'foo', 'field' => 'bar' ), array( 'ID' => 1 ) )
	 * wpdb::update( 'table', array( 'column' => 'foo', 'field' => 1337 ), array( 'ID' => 1 ), array( '%s', '%d' ), array( '%d' ) )
	 * </code>
	 *
	 * @since 2.5.0
	 * @see wpdb::prepare()
	 * @see wpdb::$field_types
	 * @see wp_set_wpdb_vars()
	 *
	 * @param string $table table name
	 * @param array $data Data to update (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
	 * @param array $where A named array of WHERE clauses (in column => value pairs). Multiple clauses will be joined with ANDs. Both $where columns and $where values should be "raw".
	 * @param array|string $format Optional. An array of formats to be mapped to each of the values in $data. If string, that format will be used for all of the values in $data.
	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
	 * @param array|string $where_format Optional. An array of formats to be mapped to each of the values in $where. If string, that format will be used for all of the items in $where. A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $where will be treated as strings.
	 * @return int|false The number of rows updated, or false on error.
	 */
	function update( $table, $data, $where, $format = null, $where_format = null ) {
		if ( ! is_array( $data ) || ! is_array( $where ) )
			return false;

		$formats = $format = (array) $format;
		$bits = $wheres = array();
		foreach ( (array) array_keys( $data ) as $field ) {
			if ( !empty( $format ) )
				$form = ( $form = array_shift( $formats ) ) ? $form : $format[0];
			elseif ( isset($this->field_types[$field]) )
				$form = $this->field_types[$field];
			else
				$form = '%s';
			$bits[] = "`$field` = {$form}";
		}

		$where_formats = $where_format = (array) $where_format;
		foreach ( (array) array_keys( $where ) as $field ) {
			if ( !empty( $where_format ) )
				$form = ( $form = array_shift( $where_formats ) ) ? $form : $where_format[0];
			elseif ( isset( $this->field_types[$field] ) )
				$form = $this->field_types[$field];
			else
				$form = '%s';
			$wheres[] = "`$field` = {$form}";
		}

		$sql = "UPDATE `$table` SET " . implode( ', ', $bits ) . ' WHERE ' . implode( ' AND ', $wheres );
		return $this->query( $this->prepare( $sql, array_merge( array_values( $data ), array_values( $where ) ) ) );
	}

	/**
	 * Delete a row in the table
	 *
	 * <code>
	 * wpdb::delete( 'table', array( 'ID' => 1 ) )
	 * wpdb::delete( 'table', array( 'ID' => 1 ), array( '%d' ) )
	 * </code>
	 *
	 * @since 3.4.0
	 * @see wpdb::prepare()
	 * @see wpdb::$field_types
	 * @see wp_set_wpdb_vars()
	 *
	 * @param string $table table name
	 * @param array $where A named array of WHERE clauses (in column => value pairs). Multiple clauses will be joined with ANDs. Both $where columns and $where values should be "raw".
	 * @param array|string $where_format Optional. An array of formats to be mapped to each of the values in $where. If string, that format will be used for all of the items in $where. A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $where will be treated as strings unless otherwise specified in wpdb::$field_types.
	 * @return int|false The number of rows updated, or false on error.
	 */
	function delete( $table, $where, $where_format = null ) {
		if ( ! is_array( $where ) )
			return false;

		$bits = $wheres = array();

		$where_formats = $where_format = (array) $where_format;

		foreach ( array_keys( $where ) as $field ) {
			if ( !empty( $where_format ) ) {
				$form = ( $form = array_shift( $where_formats ) ) ? $form : $where_format[0];
			} elseif ( isset( $this->field_types[ $field ] ) ) {
				$form = $this->field_types[ $field ];
			} else {
				$form = '%s';
			}

			$wheres[] = "$field = $form";
		}

		$sql = "DELETE FROM $table WHERE " . implode( ' AND ', $wheres );
		return $this->query( $this->prepare( $sql, $where ) );
	}


	/**
	 * Retrieve one variable from the database.
	 *
	 * Executes a SQL query and returns the value from the SQL result.
	 * If the SQL result contains more than one column and/or more than one row, this function returns the value in the column and row specified.
	 * If $query is null, this function returns the value in the specified column and row from the previous SQL result.
	 *
	 * @since 0.71
	 *
	 * @param string|null $query Optional. SQL query. Defaults to null, use the result from the previous query.
	 * @param int $x Optional. Column of value to return. Indexed from 0.
	 * @param int $y Optional. Row of value to return. Indexed from 0.
	 * @return string|null Database query result (as string), or null on failure
	 */
	function get_var( $query = null, $x = 0, $y = 0 ) {
		$this->func_call = "\$db->get_var(\"$query\", $x, $y)";
		if ( $query )
			$this->query( $query );

		// Extract var out of cached results based x,y vals
		if ( !empty( $this->last_result[$y] ) ) {
			$values = array_values( get_object_vars( $this->last_result[$y] ) );
		}

		// If there is a value return it else return null
		return ( isset( $values[$x] ) && $values[$x] !== '' ) ? $values[$x] : null;
	}

	/**
	 * Retrieve one row from the database.
	 *
	 * Executes a SQL query and returns the row from the SQL result.
	 *
	 * @since 0.71
	 *
	 * @param string|null $query SQL query.
	 * @param string $output Optional. one of ARRAY_A | ARRAY_N | OBJECT constants. Return an associative array (column => value, ...),
	 * 	a numerically indexed array (0 => value, ...) or an object ( ->column = value ), respectively.
	 * @param int $y Optional. Row to return. Indexed from 0.
	 * @return mixed Database query result in format specified by $output or null on failure
	 */
	function get_row( $query = null, $output = OBJECT, $y = 0 ) {
		$this->func_call = "\$db->get_row(\"$query\",$output,$y)";
		if ( $query )
			$this->query( $query );
		else
			return null;

		if ( !isset( $this->last_result[$y] ) )
			return null;

		if ( $output == OBJECT ) {
			return $this->last_result[$y] ? $this->last_result[$y] : null;
		} elseif ( $output == ARRAY_A ) {
			return $this->last_result[$y] ? get_object_vars( $this->last_result[$y] ) : null;
		} elseif ( $output == ARRAY_N ) {
			return $this->last_result[$y] ? array_values( get_object_vars( $this->last_result[$y] ) ) : null;
		} else {
			$this->print_error( " \$db->get_row(string query, output type, int offset) -- Output type must be one of: OBJECT, ARRAY_A, ARRAY_N" );
		}
	}

	/**
	 * Retrieve one column from the database.
	 *
	 * Executes a SQL query and returns the column from the SQL result.
	 * If the SQL result contains more than one column, this function returns the column specified.
	 * If $query is null, this function returns the specified column from the previous SQL result.
	 *
	 * @since 0.71
	 *
	 * @param string|null $query Optional. SQL query. Defaults to previous query.
	 * @param int $x Optional. Column to return. Indexed from 0.
	 * @return array Database query result. Array indexed from 0 by SQL result row number.
	 */
	function get_col( $query = null , $x = 0 ) {
		if ( $query )
			$this->query( $query );

		$new_array = array();
		// Extract the column values
		for ( $i = 0, $j = count( $this->last_result ); $i < $j; $i++ ) {
			$new_array[$i] = $this->get_var( null, $x, $i );
		}
		return $new_array;
	}

	/**
	 * Retrieve an entire SQL result set from the database (i.e., many rows)
	 *
	 * Executes a SQL query and returns the entire SQL result.
	 *
	 * @since 0.71
	 *
	 * @param string $query SQL query.
	 * @param string $output Optional. Any of ARRAY_A | ARRAY_N | OBJECT | OBJECT_K constants. With one of the first three, return an array of rows indexed from 0 by SQL result row number.
	 * 	Each row is an associative array (column => value, ...), a numerically indexed array (0 => value, ...), or an object. ( ->column = value ), respectively.
	 * 	With OBJECT_K, return an associative array of row objects keyed by the value of each row's first column's value. Duplicate keys are discarded.
	 * @return mixed Database query results
	 */
	function get_results( $query = null, $output = OBJECT ) {
		$this->func_call = "\$db->get_results(\"$query\", $output)";

		if ( $query )
			$this->query( $query );
		else
			return null;

		$new_array = array();
		if ( $output == OBJECT ) {
			// Return an integer-keyed array of row objects
			return $this->last_result;
		} elseif ( $output == OBJECT_K ) {
			// Return an array of row objects with keys from column 1
			// (Duplicates are discarded)
			foreach ( $this->last_result as $row ) {
				$var_by_ref = get_object_vars( $row );
				$key = array_shift( $var_by_ref );
				if ( ! isset( $new_array[ $key ] ) )
					$new_array[ $key ] = $row;
			}
			return $new_array;
		} elseif ( $output == ARRAY_A || $output == ARRAY_N ) {
			// Return an integer-keyed array of...
			if ( $this->last_result ) {
				foreach( (array) $this->last_result as $row ) {
					if ( $output == ARRAY_N ) {
						// ...integer-keyed row arrays
						$new_array[] = array_values( get_object_vars( $row ) );
					} else {
						// ...column name-keyed row arrays
						$new_array[] = get_object_vars( $row );
					}
				}
			}
			return $new_array;
		}
		return null;
	}

	/**
	 * Load the column metadata from the last query.
	 *
	 * @since 3.5.0
	 *
	 * @access protected
	 */
	protected function load_col_info() {
		if ( $this->col_info )
			return;

		if ( $this->use_mysqli ) {
			for ( $i = 0; $i < @mysqli_num_fields( $this->result ); $i++ ) {
				$this->col_info[ $i ] = @mysqli_fetch_field( $this->result, $i );
			}
		} else {
			for ( $i = 0; $i < @mysql_num_fields( $this->result ); $i++ ) {
				$this->col_info[ $i ] = @mysql_fetch_field( $this->result, $i );
			}
		}
	}

	/**
	 * Retrieve column metadata from the last query.
	 *
	 * @since 0.71
	 *
	 * @param string $info_type Optional. Type one of name, table, def, max_length, not_null, primary_key, multiple_key, unique_key, numeric, blob, type, unsigned, zerofill
	 * @param int $col_offset Optional. 0: col name. 1: which table the col's in. 2: col's max length. 3: if the col is numeric. 4: col's type
	 * @return mixed Column Results
	 */
	function get_col_info( $info_type = 'name', $col_offset = -1 ) {
		$this->load_col_info();

		if ( $this->col_info ) {
			if ( $col_offset == -1 ) {
				$i = 0;
				$new_array = array();
				foreach( (array) $this->col_info as $col ) {
					$new_array[$i] = $col->{$info_type};
					$i++;
				}
				return $new_array;
			} else {
				return $this->col_info[$col_offset]->{$info_type};
			}
		}
	}

	/**
	 * Starts the timer, for debugging purposes.
	 *
	 * @since 1.5.0
	 *
	 * @return true
	 */
	function timer_start() {
		$this->time_start = microtime( true );
		return true;
	}

	/**
	 * Stops the debugging timer.
	 *
	 * @since 1.5.0
	 *
	 * @return float Total time spent on the query, in seconds
	 */
	function timer_stop() {
		return ( microtime( true ) - $this->time_start );
	}

	/**
	 * Wraps errors in a nice header and footer and dies.
	 *
	 * Will not die if wpdb::$show_errors is false.
	 *
	 * @since 1.5.0
	 *
	 * @param string $message The Error message
	 * @param string $error_code Optional. A Computer readable string to identify the error.
	 * @return false|void
	 */
	function bail( $message, $error_code = '500' ) {
		if ( !$this->show_errors ) {
			if ( class_exists( 'WP_Error' ) )
				$this->error = new WP_Error($error_code, $message);
			else
				$this->error = $message;
			return false;
		}
		wp_die($message);
	}

	/**
	 * Whether MySQL database is at least the required minimum version.
	 *
	 * @since 2.5.0
	 * @uses $wp_version
	 * @uses $required_mysql_version
	 *
	 * @return WP_Error
	 */
	function check_database_version() {
		global $wp_version, $required_mysql_version;
		// Make sure the server has the required MySQL version
		if ( version_compare($this->db_version(), $required_mysql_version, '<') )
			return new WP_Error('database_version', sprintf( __( '<strong>ERROR</strong>: WordPress %1$s requires MySQL %2$s or higher' ), $wp_version, $required_mysql_version ));
	}

	/**
	 * Whether the database supports collation.
	 *
	 * Called when WordPress is generating the table scheme.
	 *
	 * @since 2.5.0
	 * @deprecated 3.5.0
	 * @deprecated Use wpdb::has_cap( 'collation' )
	 *
	 * @return bool True if collation is supported, false if version does not
	 */
	function supports_collation() {
		_deprecated_function( __FUNCTION__, '3.5', 'wpdb::has_cap( \'collation\' )' );
		return $this->has_cap( 'collation' );
	}

	/**
	 * The database character collate.
	 *
	 * @since 3.5.0
	 *
	 * @return string The database character collate.
	 */
	public function get_charset_collate() {
		$charset_collate = '';

		if ( ! empty( $this->charset ) )
			$charset_collate = "DEFAULT CHARACTER SET $this->charset";
		if ( ! empty( $this->collate ) )
			$charset_collate .= " COLLATE $this->collate";

		return $charset_collate;
	}

	/**
	 * Determine if a database supports a particular feature.
	 *
	 * @since 2.7.0
	 * @see wpdb::db_version()
	 *
	 * @param string $db_cap The feature to check for.
	 * @return bool
	 */
	function has_cap( $db_cap ) {
		$version = $this->db_version();

		switch ( strtolower( $db_cap ) ) {
			case 'collation' :    // @since 2.5.0
			case 'group_concat' : // @since 2.7.0
			case 'subqueries' :   // @since 2.7.0
				return version_compare( $version, '4.1', '>=' );
			case 'set_charset' :
				return version_compare( $version, '5.0.7', '>=' );
		};

		return false;
	}

	/**
	 * Retrieve the name of the function that called wpdb.
	 *
	 * Searches up the list of functions until it reaches
	 * the one that would most logically had called this method.
	 *
	 * @since 2.5.0
	 *
	 * @return string The name of the calling function
	 */
	function get_caller() {
		return wp_debug_backtrace_summary( __CLASS__ );
	}

	/**
	 * The database version number.
	 *
	 * @since 2.7.0
	 *
	 * @return false|string false on failure, version number on success
	 */
	function db_version() {
		if ( $this->use_mysqli ) {
			$server_info = mysqli_get_server_info( $this->dbh );
		} else {
			$server_info = mysql_get_server_info( $this->dbh );
		}
		return preg_replace( '/[^0-9.].*/', '', $server_info );
	}
}