set_url_scheme

	 *
	 * @param string $url    The complete URL including scheme and path.
	 * @param string $path   Path relative to the URL. Blank string if no path is specified.
	 * @param string $scheme The scheme to use.
	 */
	return apply_filters( 'self_admin_url', $url, $path, $scheme );
}

/**
 * Sets the scheme for a URL.
 *
 * @since 3.4.0
 * @since 4.4.0 The 'rest' scheme was added.
 *
 * @param string      $url    Absolute URL that includes a scheme
 * @param string|null $scheme Optional. Scheme to give $url. Currently 'http', 'https', 'login',
 *                            'login_post', 'admin', 'relative', 'rest', 'rpc', or null. Default null.
 * @return string URL with chosen scheme.
 */
function set_url_scheme( $url, $scheme = null ) {
	$orig_scheme = $scheme;

	if ( ! $scheme ) {
		$scheme = is_ssl() ? 'https' : 'http';
	} elseif ( 'admin' === $scheme || 'login' === $scheme || 'login_post' === $scheme || 'rpc' === $scheme ) {
		$scheme = is_ssl() || force_ssl_admin() ? 'https' : 'http';
	} elseif ( 'http' !== $scheme && 'https' !== $scheme && 'relative' !== $scheme ) {
		$scheme = is_ssl() ? 'https' : 'http';
	}

	$url = trim( $url );
	if ( substr( $url, 0, 2 ) === '//' ) {
		$url = 'http:' . $url;
	}

	if ( 'relative' === $scheme ) {
		$url = ltrim( preg_replace( '#^\w+://[^/]*#', '', $url ) );