Error in wp-admin when setting the URL to just a forward slash

[daveherman71]

I have some pages on my site that I need to redirect to the home page (due to legacy SEO).

However redirecting to "/" causes an error in wp-admin.

A PHP Error was encountered

Severity: Notice

Message: Uninitialized string offset: 1

Filename: classes/plugin.php

Line Number: 799

This is the function where the error occurs:

    public static function absolute_url( $url ) {
        // Convert server- and protocol-relative URLs to absolute URLs.
        if ( '/' === $url[0] ) {
            // Protocol-relative.
            if ( '/' === $url[1] ) {
                $url = set_url_scheme( 'http:' . $url );
            } else {
                // Host-relative.
                $url = set_url_scheme( 'http://' . $_SERVER['HTTP_HOST'] . $url );
            }
        }

        if ( 'mailto' !== parse_url( $url, PHP_URL_SCHEME ) ) {
            $url = str_replace( '@', '%40', $url );
        }

        return $url;
    }

My proposed fix is to first check the length of the string before checking if it is protocol-relative, as follows:

    public static function absolute_url( $url ) {
        // Convert server- and protocol-relative URLs to absolute URLs.
        if ( '/' === $url[0] ) {
            // Protocol-relative.
            if ( strlen($url) > 1 && '/' === $url[1] ) {
                $url = set_url_scheme( 'http:' . $url );
            } else {
                // Host-relative.
                $url = set_url_scheme( 'http://' . $_SERVER['HTTP_HOST'] . $url );
            }
        }

        if ( 'mailto' !== parse_url( $url, PHP_URL_SCHEME ) ) {
            $url = str_replace( '@', '%40', $url );
        }

        return $url;
    }