onal. Meta value to get (without prefix).
	 *
	 * @return mixed Value for the $meta if one is given, might be the default.
	 *               If no meta is given, an array of all the meta data for the term.
	 *               False if the term does not exist or the $meta provided is invalid.
	 */
	public static function get_term_meta( $term, $taxonomy, $meta = null ) {
		/* Figure out the term id. */
		if ( is_int( $term ) ) {
			$term = get_term_by( 'id', $term, $taxonomy );
		}
		elseif ( is_string( $term ) ) {
			$term = get_term_by( 'slug', $term, $taxonomy );
		}

		if ( is_object( $term ) && isset( $term->term_id ) ) {
			$term_id = $term->term_id;
		}
		else {
			return false;
		}

		$tax_meta = self::get_term_tax_meta( $term_id, $taxonomy );

		/*
		 * Either return the complete array or a single value from it or false if the value does not exist
		 * (shouldn't happen after merge with defaults, indicates typo in request).
		 */
		if ( ! isset( $meta ) ) {
			return $tax_meta;
		}

		if ( isset( $tax_meta[ 'wpseo_' . $meta ] ) ) {
			return $tax_meta[ 'wpseo_' . $meta ];
		}

		return false;
	}

	/**
	 * Get the current queried object and return the meta value.
	 *
	 * @param string $meta The meta field that is needed.
	 *
	 * @return mixed
	 */
	public static function get_meta_without_term( $meta ) {
		$term = $GLOBALS['wp_query']->get_queried_object();
		if ( ! $term || empty( $term->taxonomy ) ) {
			return false;
		}

		return self::get_term_meta( $term, $term->taxonomy, $meta );
	}

	/**
	 * Saving the values for the given term_id.
	 *
	 * @param int    $term_id     ID of the term to save data for.
	 * @param string $taxonomy    The taxonomy the term belongs to.
	 * @param array  $meta_values The values that will be saved.
	 *
	 * @return void
	 */
	public static function set_values( $term_id, $taxonomy, array $meta_values ) {
		/* Validate the post values */
		$old   = self::get_term_meta( $term_id, $taxonomy );
		$clean = self::validate_term_meta_data( $meta_values, $old );

		self::save_clean_values( $term_id, $taxonomy, $clean );
	}

	/**
	 * Setting a single value to the term meta.
	 *
	 * @param int    $term_id    ID of the term to save data for.
	 * @param string $taxonomy   The taxonomy the term belongs to.
	 * @param string $meta_key   The target meta key to store the value in.
	 * @param string $meta_value The value of the target meta key.
	 *
	 * @return void
	 */
	public static function set_value( $term_id, $taxonomy, $meta_key, $meta_value ) {

		if ( substr( strtolower( $meta_key ), 0, 6 ) !== 'wpseo_' ) {
			$meta_key = 'wpseo_' . $meta_key;
		}

		self::set_values( $term_id, $taxonomy, [ $meta_key => $meta_value ] );
	}

	/**
	 * Find the keyword usages in the metas for the taxonomies/terms.
	 *
	 * @param string $keyword          The keyword to look for.
	 * @param string $current_term_id  The current term id.
	 * @param string $current_taxonomy The current taxonomy name.
	 *
	 * @return array
	 */
	public static function get_keyword_usage( $keyword, $current_term_id, $current_taxonomy ) {
		$tax_meta = self::get_tax_meta();

		$found = [];
		// @todo Check for terms of all taxonomies, not only the current taxonomy.
		foreach ( $tax_meta as $taxonomy_name => $terms ) {
			foreach ( $terms as $term_id => $meta_values ) {
				$is_current = ( $current_taxonomy === $taxonomy_name && (string) $current_term_id === (string) $term_id );
				if ( ! $is_current && ! empty( $meta_values['wpseo_focuskw'] ) && $meta_values['wpseo_focuskw'] === $keyword ) {
					$found[] = $term_id;
				}
			}
		}

		return [ $keyword => $found ];
	}

	/**
	 * Saving the values for the given term_id.
	 *
	 * @param int    $term_id  ID of the term to save data for.
	 * @param string $taxonomy The taxonomy the term belongs to.
	 * @param array  $clean    Array with clean values.
	 *
	 * @return void
	 */
	private static function save_clean_values( $term_id, $taxonomy, array $clean ) {
		$tax_meta = self::get_tax_meta();

		/* Add/remove the result to/from the original option value. */
		if ( $clean !== [] ) {
			$tax_meta[ $taxonomy ][ $term_id ] = $clean;
		}
		else {
			unset( $tax_meta[ $taxonomy ][ $term_id ] );
			if ( isset( $tax_meta[ $taxonomy ] ) && $tax_meta[ $taxonomy ] === [] ) {
				unset( $tax_meta[ $taxonomy ] );
			}
		}

		// Prevent complete array validation.
		$tax_meta['wpseo_already_validated'] = true;

		self::save_tax_meta( $tax_meta );
	}

	/**
	 * Getting the meta from the options.
	 *
	 * @return void|array
	 */
	private static function get_tax_meta() {
		return get_option( self::$name );
	}

	/**
	 * Saving the tax meta values to the database.
	 *
	 * @param array $tax_meta Array with the meta values for taxonomy.
	 *
	 * @return void
	 */
	private static function save_tax_meta( $tax_meta ) {
		update_option( self::$name, $tax_meta );
	}

	/**
	 * Getting the taxonomy meta for the given term_id and taxonomy.
	 *
	 * @param int    $term_id  The id of the term.
	 * @param string $taxonomy Name of the taxonomy to which the term is attached.
	 *
	 * @return array
	 */
	private static function get_term_tax_meta( $term_id, $taxonomy ) {
		$tax_meta = self::get_tax_meta();

		/* If we have data for the term, merge with defaults for complete array, otherwise set defaults. */
		if ( isset( $tax_meta[ $taxonomy ][ $term_id ] ) ) {
			return array_merge( self::$defaults_per_term, $tax_meta[ $taxonomy ][ $term_id ] );
		}

		return self::$defaults_per_term;
	}
}