PHP Deprecated: usort(): Returning bool from comparison function is deprecated, return an integer less than, equal to, or greater than zero [duplicate]

I have a the warning PHP Deprecated: usort(): Returning bool from comparison function is deprecated, return an integer less than, equal to, or greater than zero from the following:

public function get_rollback() {
            $rollback = array();
            $versions = $this->get_api_versions();
            $versions = apply_filters( $this->get_key() . '_rollbacks', $versions );

            if ( $versions ) {
                usort( $versions, array( $this, 'sort_rollback_array' ) );
                foreach ( $versions as $version ) {
                    if ( isset( $version['version'] ) && isset( $version['url'] ) && version_compare( $this->version, $version['version'], '>' ) ) {
                        $rollback = $version;
                        break;
                    }
                }
            }

            return $rollback;
        }

I have tried replacing $rollback = $version; with $rollback <=> $version; with no effect.

Can anyone suggest how to rewrite to prevent the warning?