Any value other than false will short-circuit the retrieval
	 *                                   of the transient, and return that value.
	 * @param string $transient          Transient name.
	 */
	$pre = apply_filters( "pre_site_transient_{$transient}", false, $transient );

	if ( false !== $pre ) {
		return $pre;
	}

	if ( wp_using_ext_object_cache() ) {
		$value = wp_cache_get( $transient, 'site-transient' );
	} else {
		// Core transients that do not have a timeout. Listed here so querying timeouts can be avoided.
		$no_timeout       = array( 'update_core', 'update_plugins', 'update_themes' );
		$transient_option = '_site_transient_' . $transient;
		if ( ! in_array( $transient, $no_timeout, true ) ) {
			$transient_timeout = '_site_transient_timeout_' . $transient;
			$timeout           = get_site_option( $transient_timeout );
			if ( false !== $timeout && $timeout < time() ) {
				delete_site_option( $transient_option );
				delete_site_option( $transient_timeout );
				$value = false;
			}
		}

		if ( ! isset( $value ) ) {
			$value = get_site_option( $transient_option );
		}
	}

	/**
	 * Filters the value of an existing site transient.
	 *
	 * The dynamic portion of the hook name, `$transient`, refers to the transient name.
	 *
	 * @since 2.9.0
	 * @since 4.4.0 The `$transient` parameter was added.
	 *
	 * @param mixed  $value     Value of site transient.
	 * @param string $transient Transient name.
	 */
	return apply_filters( "site_transient_{$transient}", $value, $transient );
}

/**
 * Sets/updates the value of a site transient.
 *
 * You do not need to serialize values. If the value needs to be serialized,
 * then it will be serialized before it is set.
 *
 * @since 2.9.0
 *
 * @see set_transient()
 *
 * @param string $transient  Transient name. Expected to not be SQL-escaped. Must be
 *                           167 characters or fewer in length.
 * @param mixed  $value      Transient value. Expected to not be SQL-escaped.
 * @param int    $expiration Optional. Time until expiration in seconds. Default 0 (no expiration).
 * @return bool True if the value was set, false otherwise.
 */
function set_site_transient( $transient, $value, $expiration = 0 ) {

	/**
	 * Filters the value of a specific site transient before it is set.
	 *
	 * The dynamic portion of the hook name, `$transient`, refers to the transient name.
	 *
	 * @since 3.0.0
	 * @since 4.4.0 The `$transient` parameter was added.
	 *
	 * @param mixed  $value     New value of site transient.
	 * @param string $transient Transient name.
	 */
	$value = apply_filters( "pre_set_site_transient_{$transient}", $value, $transient );

	$expiration = (int) $expiration;

	/**
	 * Filters the expiration for a site transient before its value is set.
	 *
	 * The dynamic portion of the hook name, `$transient`, refers to the transient name.
	 *
	 * @since 4.4.0
	 *
	 * @param int    $expiration Time until expiration in seconds. Use 0 for no expiration.
	 * @param mixed  $value      New value of site transient.
	 * @param string $transient  Transient name.
	 */
	$expiration = apply_filters( "expiration_of_site_transient_{$transient}", $expiration, $value, $transient );

	if ( wp_using_ext_object_cache() ) {
		$result = wp_cache_set( $transient, $value, 'site-transient', $expiration );
	} else {
		$transient_timeout = '_site_transient_timeout_' . $transient;
		$option            = '_site_transient_' . $transient;

		if ( false === get_site_option( $option ) ) {
			if ( $expiration ) {
				add_site_option( $transient_timeout, time() + $expiration );
			}
			$result = add_site_option( $option, $value );
		} else {
			if ( $expiration ) {
				update_site_option( $transient_timeout, time() + $expiration );
			}
			$result = update_site_option( $option, $value );
		}
	}

	if ( $result ) {

		/**
		 * Fires after the value for a specific site transient has been set.
		 *
		 * The dynamic portion of the hook name, `$transient`, refers to the transient name.
		 *
		 * @since 3.0.0
		 * @since 4.4.0 The `$transient` parameter was added
		 *
		 * @param mixed  $value      Site transient value.
		 * @param int    $expiration Time until expiration in seconds.
		 * @param string $transient  Transient name.
		 */
		do_action( "set_site_transient_{$transient}", $value, $expiration, $transient );

		/**
		 * Fires after the value for a site transient has been set.
		 *
		 * @since 3.0.0
		 *
		 * @param string $transient  The name of the site transient.
		 * @param mixed  $value      Site transient value.
		 * @param int    $expiration Time until expiration in seconds.
		 */
		do_action( 'setted_site_transient', $transient, $value, $expiration );
	}

	return $result;
}

/**
 * Registers default settings available in WordPress.
 *
 * The settings registered here are primarily useful for the REST API, so this
 * does not encompass all settings available in WordPress.
 *
 * @since 4.7.0
 */
function register_initial_settings() {
	register_setting(
		'general',
		'blogname',
		array(
			'show_in_rest' => array(
				'name' => 'title',
			),
			'type'         => 'string',
			'description'  => __( 'Site title.' ),
		)
	);

	register_setting(
		'general',
		'blogdescription',
		array(
			'show_in_rest' => array(
				'name' => 'description',
			),
			'type'         => 'string',
			'description'  => __( 'Site tagline.' ),
		)
	);

	if ( ! is_multisite() ) {
		register_setting(
			'general',
			'siteurl',
			array(
				'show_in_rest' => array(
					'name'   => 'url',
					'schema' => array(
						'format' => 'uri',
					),
				),
				'type'         => 'string',
				'description'  => __( 'Site URL.' ),
			)
		);
	}

	if ( ! is_multisite() ) {
		register_setting(
			'general',
			'admin_email',
			array(
				'show_in_rest' => array(
					'name'   => 'email',
					'schema' => array(
						'format' => 'email',
					),
				),
				'type'         => 'string',
				'description'  => __( 'This address is used for admin purposes, like new user notification.' ),
			)
		);
	}

	register_setting(
		'general',
		'timezone_string',
		array(
			'show_in_rest' => array(
				'name' => 'timezone',
			),
			'type'         => 'string',
			'description'  => __( 'A city in the same timezone as you.' ),
		)
	);

	register_setting(
		'general',
		'date_format',
		array(
			'show_in_rest' => true,
			'type'         => 'string',
			'description'  => __( 'A date format for all date strings.' ),
		)
	);

	register_setting(
		'general',
		'time_format',
		array(
			'show_in_rest' => true,
			'type'         => 'string',
			'description'  => __( 'A time format for all time strings.' ),
		)
	);

	register_setting(
		'general',
		'start_of_week',
		array(
			'show_in_rest' => true,
			'type'         => 'integer',
			'description'  => __( 'A day number of the week that the week should start on.' ),
		)
	);

	register_setting(
		'general',
		'WPLANG',
		array(
			'show_in_rest' => array(
				'name' => 'language',
			),
			'type'         => 'string',
			'description'  => __( 'WordPress locale code.' ),
			'default'      => 'en_US',
		)
	);

	register_setting(
		'writing',
		'use_smilies',
		array(
			'show_in_rest' => true,
			'type'         => 'boolean',
			'description'  => __( 'Convert emoticons like :-) and :-P to graphics on display.' ),
			'default'      => true,
		)
	);

	register_setting(
		'writing',
		'default_category',
		array(
			'show_in_rest' => true,
			'type'         => 'integer',
			'description'  => __( 'Default post category.' ),
		)
	);

	register_setting(
		'writing',
		'default_post_format',
		array(
			'show_in_rest' => true,
			'type'         => 'string',
			'description'  => __( 'Default post format.' ),
		)
	);

	register_setting(
		'reading',
		'posts_per_page',
		array(
			'show_in_rest' => true,
			'type'         => 'integer',
			'description'  => __( 'Blog pages show at most.' ),
			'default'      => 10,
		)
	);

	register_setting(
		'discussion',
		'default_ping_status',
		array(
			'show_in_rest' => array(
				'schema' => array(
					'enum' => array( 'open', 'closed' ),
				),
			),
			'type'         => 'string',
			'description'  => __( 'Allow link notifications from other blogs (pingbacks and trackbacks) on new articles.' ),
		)
	);

	register_setting(
		'discussion',
		'default_comment_status',
		array(
			'show_in_rest' => array(
				'schema' => array(
					'enum' => array( 'open', 'closed' ),
				),
			),
			'type'         => 'string',
			'description'  => __( 'Allow people to submit comments on new posts.' ),
		)
	);
}

/**
 * Registers a setting and its data.
 *
 * @since 2.7.0
 * @since 4.7.0 `$args` can be passed to set flags on the setting, similar to `register_meta()`.
 * @since 5.5.0 `$new_whitelist_options` was renamed to `$new_allowed_options`.
 *              Please consider writing more inclusive code.
 *
 * @global array $new_allowed_options
 * @global array $wp_registered_settings
 *
 * @param string $option_group A settings group name. Should correspond to an allowed option key name.
 *                             Default allowed option key names include 'general', 'discussion', 'media',
 *                             'reading', 'writing', 'misc', 'options', and 'privacy'.
 * @param string $option_name The name of an option to sanitize and save.
 * @param array  $args {
 *     Data used to describe the setting when registered.
 *
 *     @type string     $type              The type of data associated with this setting.
 *                                         Valid values are 'string', 'boolean', 'integer', 'number', 'array', and 'object'.
 *     @type string     $description       A description of the data attached to this setting.
 *     @type callable   $sanitize_callback A callback function that sanitizes the option's value.
 *     @type bool|array $show_in_rest      Whether data associated with this setting should be included in the REST API.
 *                                         When registering complex settings, this argument may optionally be an
 *                                         array with a 'schema' key.
 *     @type mixed      $default           Default value when calling `get_option()`.
 * }
 */
function register_setting( $option_group, $option_name, $args = array() ) {
	global $new_allowed_options, $wp_registered_settings;

	/*
	 * In 5.5.0, the `$new_whitelist_options` global variable was renamed to `$new_allowed_options`.
	 * Please consider writing more inclusive code.
	 */
	$GLOBALS['new_whitelist_options'] = &$new_allowed_options;

	$defaults = array(
		'type'              => 'string',
		'group'             => $option_group,
		'description'       => '',
		'sanitize_callback' => null,
		'show_in_rest'      => false,
	);

	// Back-compat: old sanitize callback is added.
	if ( is_callable( $args ) ) {
		$args = array(
			'sanitize_callback' => $args,
		);
	}

	/**
	 * Filters the registration arguments when registering a setting.
	 *
	 * @since 4.7.0
	 *
	 * @param array  $args         Array of setting registration arguments.
	 * @param array  $defaults     Array of default arguments.
	 * @param string $option_group Setting group.
	 * @param string $option_name  Setting name.
	 */
	$args = apply_filters( 'register_setting_args', $args, $defaults, $option_group, $option_name );

	$args = wp_parse_args( $args, $defaults );

	// Require an item schema when registering settings with an array type.
	if ( false !== $args['show_in_rest'] && 'array' === $args['type'] && ( ! is_array( $args['show_in_rest'] ) || ! isset( $args['show_in_rest']['schema']['items'] ) ) ) {
		_doing_it_wrong( __FUNCTION__, __( 'When registering an "array" setting to show in the REST API, you must specify the schema for each array item in "show_in_rest.schema.items".' ), '5.4.0' );
	}

	if ( ! is_array( $wp_registered_settings ) ) {
		$wp_registered_settings = array();
	}

	if ( 'misc' === $option_group ) {
		_deprecated_argument(
			__FUNCTION__,
			'3.0.0',
			sprintf(
				/* translators: %s: misc */
				__( 'The "%s" options group has been removed. Use another settings group.' ),
				'misc'
			)
		);
		$option_group = 'general';
	}

	if ( 'privacy' === $option_group ) {
		_deprecated_argument(
			__FUNCTION__,
			'3.5.0',
			sprintf(
				/* translators: %s: privacy */
				__( 'The "%s" options group has been removed. Use another settings group.' ),
				'privacy'
			)
		);
		$option_group = 'reading';
	}

	$new_allowed_options[ $option_group ][] = $option_name;

	if ( ! empty( $args['sanitize_callback'] ) ) {
		add_filter( "sanitize_option_{$option_name}", $args['sanitize_callback'] );
	}
	if ( array_key_exists( 'default', $args ) ) {
		add_filter( "default_option_{$option_name}", 'filter_default_option', 10, 3 );
	}

	/**
	 * Fires immediately before the setting is registered but after its filters are in place.
	 *
	 * @since 5.5.0
	 *
	 * @param string $option_group Setting group.
	 * @param string $option_name  Setting name.
	 * @param array  $args         Array of setting registration arguments.
	 */
	do_action( 'register_setting', $option_group, $option_name, $args );

	$wp_registered_settings[ $option_name ] = $args;
}

/**
 * Unregisters a setting.
 *
 * @since 2.7.0
 * @since 4.7.0 `$sanitize_callback` was deprecated. The callback from `register_setting()` is now used instead.
 * @since 5.5.0 `$new_whitelist_options` was renamed to `$new_allowed_options`.
 *              Please consider writing more inclusive code.
 *
 * @global array $new_allowed_options
 * @global array $wp_registered_settings
 *
 * @param string          $option_group The settings group name used during registration.
 * @param string          $option_name  The name of the option to unregister.
 * @param callable|string $deprecated   Deprecated.
 */
function unregister_setting( $option_group, $option_name, $deprecated = '' ) {
	global $new_allowed_options, $wp_registered_settings;

	/*
	 * In 5.5.0, the `$new_whitelist_options` global variable was renamed to `$new_allowed_options`.
	 * Please consider writing more inclusive code.
	 */
	$GLOBALS['new_whitelist_options'] = &$new_allowed_options;

	if ( 'misc' === $option_group ) {
		_deprecated_argument(
			__FUNCTION__,
			'3.0.0',
			sprintf(
				/* translators: %s: misc */
				__( 'The "%s" options group has been removed. Use another settings group.' ),
				'misc'
			)
		);
		$option_group = 'general';
	}

	if ( 'privacy' === $option_group ) {
		_deprecated_argument(
			__FUNCTION__,
			'3.5.0',
			sprintf(
				/* translators: %s: privacy */
				__( 'The "%s" options group has been removed. Use another settings group.' ),
				'privacy'
			)
		);
		$option_group = 'reading';
	}

	$pos = array_search( $option_name, (array) $new_allowed_options[ $option_group ], true );

	if ( false !== $pos ) {
		unset( $new_allowed_options[ $option_group ][ $pos ] );
	}

	if ( '' !== $deprecated ) {
		_deprecated_argument(
			__FUNCTION__,
			'4.7.0',
			sprintf(
				/* translators: 1: $sanitize_callback, 2: register_setting() */
				__( '%1$s is deprecated. The callback from %2$s is used instead.' ),
				'<code>$sanitize_callback</code>',
				'<code>register_setting()</code>'
			)
		);
		remove_filter( "sanitize_option_{$option_name}", $deprecated );
	}

	if ( isset( $wp_registered_settings[ $option_name ] ) ) {
		// Remove the sanitize callback if one was set during registration.
		if ( ! empty( $wp_registered_settings[ $option_name ]['sanitize_callback'] ) ) {
			remove_filter( "sanitize_option_{$option_name}", $wp_registered_settings[ $option_name ]['sanitize_callback'] );
		}

		// Remove the default filter if a default was provided during registration.
		if ( array_key_exists( 'default', $wp_registered_settings[ $option_name ] ) ) {
			remove_filter( "default_option_{$option_name}", 'filter_default_option', 10 );
		}

		/**
		 * Fires immediately before the setting is unregistered and after its filters have been removed.
		 *
		 * @since 5.5.0
		 *
		 * @param string $option_group Setting group.
		 * @param string $option_name  Setting name.
		 */
		do_action( 'unregister_setting', $option_group, $option_name );

		unset( $wp_registered_settings[ $option_name ] );
	}
}

/**
 * Retrieves an array of registered settings.
 *
 * @since 4.7.0
 *
 * @global array $wp_registered_settings
 *
 * @return array List of registered settings, keyed by option name.
 */
function get_registered_settings() {
	global $wp_registered_settings;

	if ( ! is_array( $wp_registered_settings ) ) {
		return array();
	}

	return $wp_registered_settings;
}

/**
 * Filters the default value for the option.
 *
 * For settings which register a default setting in `register_setting()`, this
 * function is added as a filter to `default_option_{$option}`.
 *
 * @since 4.7.0
 *
 * @param mixed  $default        Existing default value to return.
 * @param string $option         Option name.
 * @param bool   $passed_default Was `get_option()` passed a default value?
 * @return mixed Filtered default value.
 */
function filter_default_option( $default, $option, $passed_default ) {
	if ( $passed_default ) {
		return $default;
	}

	$registered = get_registered_settings();
	if ( empty( $registered[ $option ] ) ) {
		return $default;
	}

	return $registered[ $option ]['default'];
}