How to implement breakpoint resumption in FTP server through PHP

How to implement breakpoint resume transfer in FTP server through PHP

With the increasing demand for network transmission, the breakpoint resume function has become very important in file transfer. Whether you are uploading or downloading large files, resuming uploads can save time and bandwidth. In PHP, we can use the FTP function library and some custom code to implement the breakpoint resume function in the FTP server. The following is a sample code on how to implement breakpoint resumption in FTP server in PHP:

1. Configuring FTP connection parameters

First, we need to set up the connection to the FTP server Parameters, including the host name, user name, password and port number of the FTP server. In PHP, we can use the ftp_connect() function to establish a connection with the FTP server and the ftp_login() function for login verification. The sample code is as follows:

$ftp_server = 'ftp.example.com';
$ftp_username = 'username';
$ftp_password = 'password';
$ftp_port = 21;

$ftp_conn = ftp_connect($ftp_server, $ftp_port);
$ftp_login = ftp_login($ftp_conn, $ftp_username, $ftp_password);

if (!$ftp_conn || !$ftp_login) {
    die('FTP connection failed');
}

2. Check whether the remote file exists

Before resuming the upload, we need to check whether the remote file exists. If the remote file exists, we can calculate the starting position that needs to be resumed based on the size of the downloaded file. In PHP, we can use the ftp_size() function to get the size of the remote file. The sample code is as follows:

$remote_file = '/path/to/remote/file.ext';
$local_file = '/path/to/local/file.ext';

if (ftp_size($ftp_conn, $remote_file) !== -1) {
    $resume_pos = filesize($local_file);
} else {
    $resume_pos = 0;
}

3. Set the starting position of resumed transmission

According to the previous calculation, we can set the starting position of resumed transmission as Downloaded file size. In PHP, we can use the ftp_raw() function to send specific FTP commands to set the starting position of the breakpoint resume transfer. The sample code is as follows:

$command = "REST $resume_pos";
ftp_raw($ftp_conn, $command);

4. Download remote files

After completing the setting of breakpoint resumption, we can use the ftp_fget() function to Download remote files. In PHP, the ftp_fget() function can write part of the remote file to the local file, and can also control the starting position of the download. The sample code is as follows:

$local_file_handle = fopen($local_file, 'ab');
$remote_file_handle = fopen("ftp://$ftp_username:$ftp_password@$ftp_server/$remote_file", 'rb');

if ($local_file_handle && $remote_file_handle) {
    fseek($local_file_handle, $resume_pos);

    while (!feof($remote_file_handle)) {
        fwrite($local_file_handle, fread($remote_file_handle, 1024));
    }

    fclose($remote_file_handle);
    fclose($local_file_handle);
}

In summary, through the above four steps, we can implement the breakpoint resume function in the FTP server in PHP. This can help us save time and bandwidth and improve the efficiency of file transfer. You can adjust and improve the code according to actual needs to achieve a more flexible and efficient breakpoint resume function.

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