rn $url;
	}

	return false;
}

/**
 * Marks allowed redirect hosts safe for HTTP requests as well.
 *
 * Attached to the {@see 'http_request_host_is_external'} filter.
 *
 * @since 3.6.0
 *
 * @param bool   $is_external
 * @param string $host
 * @return bool
 */
function allowed_http_request_hosts( $is_external, $host ) {
	if ( ! $is_external && wp_validate_redirect( 'http://' . $host ) ) {
		$is_external = true;
	}
	return $is_external;
}

/**
 * Adds any domain in a multisite installation for safe HTTP requests to the
 * allowed list.
 *
 * Attached to the {@see 'http_request_host_is_external'} filter.
 *
 * @since 3.6.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param bool   $is_external
 * @param string $host
 * @return bool
 */
function ms_allowed_http_request_hosts( $is_external, $host ) {
	global $wpdb;
	static $queried = array();
	if ( $is_external ) {
		return $is_external;
	}
	if ( get_network()->domain === $host ) {
		return true;
	}
	if ( isset( $queried[ $host ] ) ) {
		return $queried[ $host ];
	}
	$queried[ $host ] = (bool) $wpdb->get_var( $wpdb->prepare( "SELECT domain FROM $wpdb->blogs WHERE domain = %s LIMIT 1", $host ) );
	return $queried[ $host ];
}

/**
 * A wrapper for PHP's parse_url() function that handles consistency in the return values
 * across PHP versions.
 *
 * Across various PHP versions, schemeless URLs containing a ":" in the query
 * are being handled inconsistently. This function works around those differences.
 *
 * @since 4.4.0
 * @since 4.7.0 The `$component` parameter was added for parity with PHP's `parse_url()`.
 *
 * @link https://www.php.net/manual/en/function.parse-url.php
 *
 * @param string $url       The URL to parse.
 * @param int    $component The specific component to retrieve. Use one of the PHP
 *                          predefined constants to specify which one.
 *                          Defaults to -1 (= return all parts as an array).
 * @return mixed False on parse failure; Array of URL components on success;
 *               When a specific component has been requested: null if the component
 *               doesn't exist in the given URL; a string or - in the case of
 *               PHP_URL_PORT - integer when it does. See parse_url()'s return values.
 */
function wp_parse_url( $url, $component = -1 ) {
	$to_unset = array();
	$url      = (string) $url;

	if ( str_starts_with( $url, '//' ) ) {
		$to_unset[] = 'scheme';
		$url        = 'placeholder:' . $url;
	} elseif ( str_starts_with( $url, '/' ) ) {
		$to_unset[] = 'scheme';
		$to_unset[] = 'host';
		$url        = 'placeholder://placeholder' . $url;
	}

	$parts = parse_url( $url );

	if ( false === $parts ) {
		// Parsing failure.
		return $parts;
	}

	// Remove the placeholder values.
	foreach ( $to_unset as $key ) {
		unset( $parts[ $key ] );
	}

	return _get_component_from_parsed_url_array( $parts, $component );
}

/**
 * Retrieves a specific component from a parsed URL array.
 *
 * @internal
 *
 * @since 4.7.0
 * @access private
 *
 * @link https://www.php.net/manual/en/function.parse-url.php
 *
 * @param array|false $url_parts The parsed URL. Can be false if the URL failed to parse.
 * @param int         $component The specific component to retrieve. Use one of the PHP
 *                               predefined constants to specify which one.
 *                               Defaults to -1 (= return all parts as an array).
 * @return mixed False on parse failure; Array of URL components on success;
 *               When a specific component has been requested: null if the component
 *               doesn't exist in the given URL; a string or - in the case of
 *               PHP_URL_PORT - integer when it does. See parse_url()'s return values.
 */
function _get_component_from_parsed_url_array( $url_parts, $component = -1 ) {
	if ( -1 === $component ) {
		return $url_parts;
	}

	$key = _wp_translate_php_url_constant_to_key( $component );
	if ( false !== $key && is_array( $url_parts ) && isset( $url_parts[ $key ] ) ) {
		return $url_parts[ $key ];
	} else {
		return null;
	}
}

/**
 * Translates a PHP_URL_* constant to the named array keys PHP uses.
 *
 * @internal
 *
 * @since 4.7.0
 * @access private
 *
 * @link https://www.php.net/manual/en/url.constants.php
 *
 * @param int $constant PHP_URL_* constant.
 * @return string|false The named key or false.
 */
function _wp_translate_php_url_constant_to_key( $constant ) {
	$translation = array(
		PHP_URL_SCHEME   => 'scheme',
		PHP_URL_HOST     => 'host',
		PHP_URL_PORT     => 'port',
		PHP_URL_USER     => 'user',
		PHP_URL_PASS     => 'pass',
		PHP_URL_PATH     => 'path',
		PHP_URL_QUERY    => 'query',
		PHP_URL_FRAGMENT => 'fragment',
	);

	if ( isset( $translation[ $constant ] ) ) {
		return $translation[ $constant ];
	} else {
		return false;
	}
}