ountry code.
	 *
	 * @since 5.4.3
	 *
	 * @param string $alpha3_code ISO 3166-alpha3 country code
	 * @return string ISO 3166-numeric country code
	 */
	public static function alpha3_to_numeric( $alpha3_code ) {
		return self::alpha2_to_numeric( self::alpha3_to_alpha2( $alpha3_code ) );
	}


	/**
	 * Converts an ISO 3166-alpha3 country code to a calling code.
	 *
	 * @since 5.4.3
	 *
	 * @param string $alpha3_code ISO 3166-alpha3 country code
	 * @return string calling code
	 */
	public static function alpha3_to_calling_code( $alpha3_code ) {
		return self::alpha2_to_calling_code( self::alpha3_to_alpha2( $alpha3_code ) );
	}


	/**
	 * Converts an ISO 3166-numeric country code to an ISO 3166-alpha2 code.
	 *
	 * @since 5.4.3
	 *
	 * @param string $numeric ISO 3166-numeric country code
	 * @return string ISO 3166-alpha2 country code
	 */
	public static function numeric_to_alpha2( $numeric ) {

		$codes = array_flip( self::$numeric );

		return $codes[$numeric] ?? '';
	}


	/**
	 * Converts an ISO 3166-numeric country code to an ISO 3166-alpha3 code.
	 *
	 * @since 5.4.3
	 *
	 * @param string $numeric ISO 3166-numeric country code
	 * @return string ISO 3166-alpha3 country code
	 */
	public static function numeric_to_alpha3( $numeric ) {
		return self::alpha2_to_alpha3( self::numeric_to_alpha2( $numeric ) );
	}


	/**
	 * Converts an ISO 3166-numeric country code to a calling code.
	 *
	 * @since 5.4.3
	 *
	 * @param string $numeric ISO 3166-numeric country code
	 * @return string calling code
	 */
	public static function numeric_to_calling_code( $numeric ) {
		return self::alpha2_to_calling_code( self::numeric_to_alpha2( $numeric ) );
	}


	/**
	 * Converts a country calling code to an ISO 3166-alpha2 code.
	 *
	 * @since 5.4.3
	 *
	 * @param string $calling_code country calling code (includes leading '+')
	 * @return string ISO 3166-alpha2 code
	 */
	public static function calling_code_to_alpha2( $calling_code ) {

		$flipped_calling_codes = self::get_flipped_calling_codes();

		return $flipped_calling_codes[$calling_code] ?? '';
	}


	/**
	 * Converts a country calling code to an ISO 3166-alpha3 code.
	 *
	 * @since 5.4.3
	 *
	 * @param string $calling_code country calling code (includes leading '+')
	 * @return string ISO 3166-alpha3 code
	 */
	public static function calling_code_to_alpha3( $calling_code ) {

		return self::alpha2_to_alpha3( self::calling_code_to_alpha2( $calling_code ) );
	}


	/**
	 * Converts a country calling code to an ISO 3166-numeric code.
	 *
	 * @since 5.4.3
	 *
	 * @param string $calling_code country calling code (includes leading '+')
	 * @return string ISO 3166-numeric code
	 */
	public static function calling_code_to_numeric( $calling_code ) {

		return self::alpha2_to_numeric( self::calling_code_to_alpha2( $calling_code ) );
	}


	/**
	 * Gets the flipped version of the calling codes array.
	 *
	 * Since array_flip will fail on the calling codes array due to
	 * having some arrays as values, this custom function is necessary.
	 *
	 * @since 5.4.3
	 *
	 * @return array
	 */
	public static function get_flipped_calling_codes() {

		if ( null === self::$flipped_calling_codes ) {

			$flipped_calling_codes = [];

			foreach ( self::$calling_codes as $alpha2 => $calling_code ) {

				if ( is_array( $calling_code ) ) {

					foreach ( $calling_code as $sub_code ) {

						$flipped_calling_codes[ $sub_code ] = $alpha2;
					}
				} else {

					$flipped_calling_codes[ $calling_code ] = $alpha2;
				}
			}

			self::$flipped_calling_codes = $flipped_calling_codes;
		}

		return self::$flipped_calling_codes;
	}


}