问PHP ftp_put函数文件限制？

EN

    set_time_limit(0);
    error_reporting( E_ALL );


    $chunksize=20;          # set to 50
    $use_ftp_cmds=false;    # set as true to actually attempt FTP commands

    $ftp_host='ftp.example.com';
    $ftp_send_to='httpdocs/abs/';


    /* find all files in directory */
    $dir = __DIR__ . '/critical_logs/';
    $files = glob( $dir . '*.*' );

    /* create, if it does not exist, a log to record the files - in parent directory */
    chdir('..\\');
    $log = getcwd() . '/files.txt';

    /* add record for each file */
    if( !file_exists( $log ) ){
        foreach( $files as $file ){
            file_put_contents( $log, $file . PHP_EOL, FILE_APPEND );
        }
    }
    /* process the file in chunks */
    if( file_exists( $log ) ){
        clearstatcache();

        $lines = file( $log, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES );
        if( count( $lines ) > 0 ){

            $chunks = array_chunk( $lines, $chunksize );

            /* connect to FTP server */
            if( $use_ftp_cmds ){

                $conn = ftp_connect( $ftp_host );
                if( !$conn ) die( sprintf( '%s connect error', $ftp_host ) );

                $login_result = ftp_login( $conn, $ftp_user_name, $ftp_user_pass );
                if( !$login_result ) die( 'Failed to login to FTP server' );
            }





            /* Process the first chunk */
            $chunk = array_shift( $chunks );

            foreach( $chunk as $file ){
                /* ftp cmds */
                $result = $use_ftp_cmds ? ftp_put( $conn, $file, sprintf( '%s/%s', $ftp_send_to, $file ) , FTP_ASCII ) : true;
                if( $result ){
                    /* remove the line from the source file and save updated version */
                    array_splice( $lines, array_search( $file, $lines ), 1 );
                }
            }


            file_put_contents( $log, '' );

            foreach( $lines as $line ){
                file_put_contents( $log, $line . PHP_EOL, FILE_APPEND );
            }

        } else {
            printf('The file %s is empty',$log);
        }
    }