ftp文件关闭操作出错

I'm using php to access file by ftp. My file read function is:

function _rfile ($file = null) {
        if ( is_readable($file) ) {
            if ( !($fh = fopen($file, 'r')) ) return false;
            $data = fread($fh, filesize($file));
            fclose($fh);
            return $data;
        }
        return false;
    }

I am getting an error on file close operation in this function with one of my ftp host.

error:

fclose(): FTP server error 550:550 The specified network name is no longer available.

This function worked fine for some other ftp host's.

Could smb advice a solution?

It may due to the access permission settings.

Please look at this link. http://forums.iis.net/t/1107644.aspx