Services_JSON::substr8

    function substr8( $string, $start, $length=false ) 
    {
        _deprecated_function( __METHOD__, '5.3.0', 'The PHP native JSON extension' );

        if ( $length === false ) {
            $length = $this->strlen8( $string ) - $start;
        }
        if ( $this->_mb_substr ) {
            return mb_substr( $string, $start, $length, "8bit" );
        }
        return substr( $string, $start, $length );
    }