an_option( $option_value, $current_version = null, $all_old_option_values = null ) {
		static $original = null;

		// Double-run this function to ensure renaming of the taxonomy options will work.
		if ( ! isset( $original )
			&& has_action( 'wpseo_double_clean_titles', [ $this, 'clean' ] ) === false
		) {
			add_action( 'wpseo_double_clean_titles', [ $this, 'clean' ] );
			$original = $option_value;
		}

		/*
		 * Move options from very old option to this one.
		 *
		 * {@internal Don't rename to the 'current' names straight away as that would prevent
		 *            the rename/unset combi below from working.}}
		 *
		 * @todo [JRF] Maybe figure out a smarter way to deal with this.
		 */
		$old_option = null;
		if ( isset( $all_old_option_values ) ) {
			// Ok, we have an import.
			if ( isset( $all_old_option_values['wpseo_indexation'] ) && is_array( $all_old_option_values['wpseo_indexation'] ) && $all_old_option_values['wpseo_indexation'] !== [] ) {
				$old_option = $all_old_option_values['wpseo_indexation'];
			}
		}
		else {
			$old_option = get_option( 'wpseo_indexation' );
		}
		if ( is_array( $old_option ) && $old_option !== [] ) {
			$move = [
				'noindexauthor'     => 'noindex-author',
				'disableauthor'     => 'disable-author',
				'noindexdate'       => 'noindex-archive',
				'noindexcat'        => 'noindex-category',
				'noindextag'        => 'noindex-post_tag',
				'noindexpostformat' => 'noindex-post_format',
			];
			foreach ( $move as $old => $new ) {
				if ( isset( $old_option[ $old ] ) && ! isset( $option_value[ $new ] ) ) {
					$option_value[ $new ] = $old_option[ $old ];
				}
			}
			unset( $move, $old, $new );
		}
		unset( $old_option );


		// Fix wrongness created by buggy version 1.2.2.
		if ( isset( $option_value['title-home'] ) && $option_value['title-home'] === '%%sitename%% - %%sitedesc%% - 12345' ) {
			$option_value['title-home-wpseo'] = '%%sitename%% - %%sitedesc%%';
		}


		/*
		 * Renaming these options to avoid ever overwritting these if a (bloody stupid) user /
		 * programmer would use any of the following as a custom post type or custom taxonomy:
		 * 'home', 'author', 'archive', 'search', '404', 'subpages'.
		 *
		 * Similarly, renaming the tax options to avoid a custom post type and a taxonomy
		 * with the same name occupying the same option.
		 */
		$rename = [
			'title-home'       => 'title-home-wpseo',
			'title-author'     => 'title-author-wpseo',
			'title-archive'    => 'title-archive-wpseo',
			'title-search'     => 'title-search-wpseo',
			'title-404'        => 'title-404-wpseo',
			'metadesc-home'    => 'metadesc-home-wpseo',
			'metadesc-author'  => 'metadesc-author-wpseo',
			'metadesc-archive' => 'metadesc-archive-wpseo',
			'noindex-author'   => 'noindex-author-wpseo',
			'noindex-archive'  => 'noindex-archive-wpseo',
		];
		foreach ( $rename as $old => $new ) {
			if ( isset( $option_value[ $old ] ) && ! isset( $option_value[ $new ] ) ) {
				$option_value[ $new ] = $option_value[ $old ];
				unset( $option_value[ $old ] );
			}
		}
		unset( $rename, $old, $new );


		/*
		 * {@internal This clean-up action can only be done effectively once the taxonomies
		 *            and post_types have been registered, i.e. at the end of the init action.}}
		 */
		if ( isset( $original ) && current_filter() === 'wpseo_double_clean_titles' || did_action( 'wpseo_double_clean_titles' ) > 0 ) {
			$rename = [
				'title-'           => 'title-tax-',
				'metadesc-'        => 'metadesc-tax-',
				'noindex-'         => 'noindex-tax-',
				'tax-hideeditbox-' => 'hideeditbox-tax-',

			];

			$taxonomy_names  = get_taxonomies( [ 'public' => true ], 'names' );
			$post_type_names = get_post_types( [ 'public' => true ], 'names' );
			$defaults        = $this->get_defaults();
			if ( $taxonomy_names !== [] ) {
				foreach ( $taxonomy_names as $tax ) {
					foreach ( $rename as $old_prefix => $new_prefix ) {
						if (
							( isset( $original[ $old_prefix . $tax ] ) && ! isset( $original[ $new_prefix . $tax ] ) )
							&& ( ! isset( $option_value[ $new_prefix . $tax ] )
								|| ( isset( $option_value[ $new_prefix . $tax ] )
									&& $option_value[ $new_prefix . $tax ] === $defaults[ $new_prefix . $tax ] ) )
						) {
							$option_value[ $new_prefix . $tax ] = $original[ $old_prefix . $tax ];

							/*
							 * Check if there is a cpt with the same name as the tax,
							 * if so, we should make sure that the old setting hasn't been removed.
							 */
							if ( ! isset( $post_type_names[ $tax ] ) && isset( $option_value[ $old_prefix . $tax ] ) ) {
								unset( $option_value[ $old_prefix . $tax ] );
							}
							else {
								if ( isset( $post_type_names[ $tax ] ) && ! isset( $option_value[ $old_prefix . $tax ] ) ) {
									$option_value[ $old_prefix . $tax ] = $original[ $old_prefix . $tax ];
								}
							}

							if ( $old_prefix === 'tax-hideeditbox-' ) {
								unset( $option_value[ $old_prefix . $tax ] );
							}
						}
					}
				}
			}
			unset( $rename, $taxonomy_names, $post_type_names, $defaults, $tax, $old_prefix, $new_prefix );
		}

		/*
		 * Make sure the values of the variable option key options are cleaned as they
		 * may be retained and would not be cleaned/validated then.
		 */
		if ( is_array( $option_value ) && $option_value !== [] ) {
			foreach ( $option_value as $key => $value ) {
				$switch_key = $this->get_switch_key( $key );

				// Similar to validation routine - any changes made there should be made here too.
				switch ( $switch_key ) {
					/* Text fields. */
					case 'title-':
					case 'metadesc-':
					case 'bctitle-ptarchive-':
						$option_value[ $key ] = WPSEO_Utils::sanitize_text_field( $value );
						break;

					case 'separator':
						if ( ! array_key_exists( $value, $this->get_separator_options() ) ) {
							$option_value[ $key ] = false;
						}
						break;

					/*
					 * Boolean fields.
					 */

					/*
					 * Covers:
					 *  'noindex-'
					 *  'hideeditbox-'
					 */
					default:
						$option_value[ $key ] = WPSEO_Utils::validate_bool( $value );
						break;
				}
			}
			unset( $key, $value, $switch_key );
		}

		return $option_value;
	}

	/**
	 * Make sure that any set option values relating to post_types and/or taxonomies are retained,
	 * even when that post_type or taxonomy may not yet have been registered.
	 *
	 * {@internal Overrule the abstract class version of this to make sure one extra renamed
	 *            variable key does not get removed. IMPORTANT: keep this method in line with
	 *            the parent on which it is based!}}
	 *
	 * @param array $dirty Original option as retrieved from the database.
	 * @param array $clean Filtered option where any options which shouldn't be in our option
	 *                     have already been removed and any options which weren't set
	 *                     have been set to their defaults.
	 *
	 * @return array
	 */
	protected function retain_variable_keys( $dirty, $clean ) {
		if ( ( is_array( $this->variable_array_key_patterns ) && $this->variable_array_key_patterns !== [] ) && ( is_array( $dirty ) && $dirty !== [] ) ) {

			// Add the extra pattern.
			$patterns   = $this->variable_array_key_patterns;
			$patterns[] = 'tax-hideeditbox-';

			/**
			 * Allow altering the array with variable array key patterns.
			 *
			 * @api  array  $patterns  Array with the variable array key patterns.
			 */
			$patterns = apply_filters( 'wpseo_option_titles_variable_array_key_patterns', $patterns );

			foreach ( $dirty as $key => $value ) {

				// Do nothing if already in filtered option array.
				if ( isset( $clean[ $key ] ) ) {
					continue;
				}

				foreach ( $patterns as $pattern ) {
					if ( strpos( $key, $pattern ) === 0 ) {
						$clean[ $key ] = $value;
						break;
					}
				}
			}
		}

		return $clean;
	}

	/**
	 * Retrieves a list of separator options.
	 *
	 * @return array An array of the separator options.
	 */
	protected static function get_separator_option_list() {
		$separators = [
			'sc-dash'   => [
				'option' => '-',
				'label'  => __( 'Dash', 'wordpress-seo' ),
			],
			'sc-ndash'  => [
				'option' => '–',
				'label'  => __( 'En dash', 'wordpress-seo' ),
			],
			'sc-mdash'  => [
				'option' => '—',
				'label'  => __( 'Em dash', 'wordpress-seo' ),
			],
			'sc-colon'  => [
				'option' => ':',
				'label'  => __( 'Colon', 'wordpress-seo' ),
			],
			'sc-middot' => [
				'option' => '·',
				'label'  => __( 'Middle dot', 'wordpress-seo' ),
			],
			'sc-bull'   => [
				'option' => '•',
				'label'  => __( 'Bullet', 'wordpress-seo' ),
			],
			'sc-star'   => [
				'option' => '*',
				'label'  => __( 'Asterisk', 'wordpress-seo' ),
			],
			'sc-smstar' => [
				'option' => '⋆',
				'label'  => __( 'Low asterisk', 'wordpress-seo' ),
			],
			'sc-pipe'   => [
				'option' => '|',
				'label'  => __( 'Vertical bar', 'wordpress-seo' ),
			],
			'sc-tilde'  => [
				'option' => '~',
				'label'  => __( 'Small tilde', 'wordpress-seo' ),
			],
			'sc-laquo'  => [
				'option' => '«',
				'label'  => __( 'Left angle quotation mark', 'wordpress-seo' ),
			],
			'sc-raquo'  => [
				'option' => '»',
				'label'  => __( 'Right angle quotation mark', 'wordpress-seo' ),
			],
			'sc-lt'     => [
				'option' => '<',
				'label'  => __( 'Less than sign', 'wordpress-seo' ),
			],
			'sc-gt'     => [
				'option' => '>',
				'label'  => __( 'Greater than sign', 'wordpress-seo' ),
			],
		];

		/**
		 * Allows altering the separator options array.
		 *
		 * @api array $separators Array with the separator options.
		 */
		$separator_list = apply_filters( 'wpseo_separator_option_list', $separators );

		if ( ! is_array( $separator_list ) ) {
			return $separators;
		}

		return $separator_list;
	}
}