This guide is for developers looking to understand and use SFTP (a secure protocol for file transfers) with PHP. The focus will be on the PHP Secure Communications Library (phpseclib), a robust library that provides an easy-to-use interface for secure communications in PHP. It supports a broad range of cryptographic operations, including SSH2 (SFTP), RSA, and symmetric encryption.
Here's an article
detailing why we prefer to use phpseclib as our PHP SFTP library.
Basically, it's an SFTP client written in pure PHP. In case you don't want to spend your time managing SFTP servers,
SFTPCloud
can do this for you on autopilot.
Getting Started with phpseclib
Before we go further into the details of using phpseclib for SFTP, let's ensure it's installed and ready to use. The recommended way to install phpseclib is through Composer, a dependency management tool for PHP. If you haven't installed Composer yet, you can download it from the official website.
Once Composer is installed, navigate to your project directory and install phpseclib by running the following command:
composer require phpseclib/phpseclib:~3.0
Connecting to a remote server via SFTP
With phpseclib installed, we can now create an SFTP connection to a remote server. To connect to an SFTP server using phpseclib as the SFTP client, you'll need the server's hostname (or IP address), a valid username, and password or SSH key pair. Here's a basic example of connecting using a username and password:
<?php
require_once('vendor/autoload.php');
use phpseclib3\Net\SFTP;
$host = 'eu-central-1.sftpcloud.io';
$user = 'my-sftp-user';
$password = 'my-sftp-user-password';
$sftp = new SFTP($host);
if (!$sftp->login($user, $password)) {
throw new \Exception('Could not initialize SFTP subsystem.');
}
echo 'Login successful';
SFTP file operations with PHP
The primary purpose of SFTP is to perform file operations on a remote server securely. Let's discuss some of the most common operations and how to perform them using PHP.
Uploading a file
To upload a local file to the server, use the
put
method:
<?php
// ...
$file_to_upload = '/path/to/local/file.txt';
$remote_file_path = '/path/to/remote/directory/file.txt';
$sftp->put($remote_file_path, $file_to_upload, SFTP::SOURCE_LOCAL_FILE);
<?php
// ...
$file_contents = 'This string will be uploaded';
$remote_file_path = '/path/to/remote/directory/file.txt';
$sftp->put($remote_file_path, $file_coontents, SFTP::SOURCE_STRING);
Downloading a file
Downloading a file is as simple as uploading. Use the
get
method, which accepts two parameters:
$remote_file_path
: The path to the file on the SFTP server that you want to download. This should include the full path to the file, including the filename and its extension.
$local_file_path
: The path on the local system where the downloaded file should be saved. This should also include the filename and extension that you want for the downloaded file.
<?php
// ...
$remote_file_path = '/path/to/remote/file.txt';
$local_file_path = '/path/to/local/directory/file.txt';
$sftp->get($remote_file_path, $local_file_path);
Deleting files
To delete a file, use the
delete
method. The method accepts one parameter: the path to the file you want to delete. This should be the full path to the file on the SFTP server.
<?php
// ...
$file_to_delete = '/path/to/remote/file.txt';
$sftp->delete($file_to_delete);
Renaming a file
In your daily operations, you may need to rename a file on your SFTP server. The
rename
method provided by the phpseclib library is designed for this purpose. This function accepts two parameters: the current name (path included) of the file and the new name (with path) that you want to give to the file. Here's an example:
<?php
// ...
$old_name = '/path/to/remote/file.txt';
$new_name = '/path/to/remote/newfile.txt';
$sftp->rename($old_name, $new_name);
<?php
// ...
$old_name = '/path/to/remote/file.txt';
$new_name = '/path/to/remote/newfile.txt';
try {
$sftp->rename($old_name, $new_name);
} catch (\Exception $e) {
echo 'Error renaming file: ' . $e->getMessage();
}
Listing all the files and directories
An essential aspect of managing your SFTP server is being able to list all the files and directories in a particular location. The phpseclib library provides the
nlist
and
rawlist
methods for this purpose.
Let's start with the
nlist
method, which provides a simple array of filenames.
<?php
// ...
$directory = '/path/to/remote/directory';
$file_list = $sftp->nlist($directory);
<?php
// ...
$directory = '/path/to/remote/directory';
$file_list = $sftp->rawlist($directory);
<?php
// ...
$directory = '/path/to/remote/directory';
try {
$file_list = $sftp->nlist($directory);
if ($file_list === false) {
throw new Exception('Error listing files in directory: ' . $directory);
}
print_r($file_list);
} catch (\Exception $e) {
echo $e->getMessage();
}
Changing directories
Sometimes, you might need to change the current working directory on the SFTP server. For example, you might need to navigate to a specific directory to upload or download files, or perform operations like listing files or creating new directories. phpseclib's
SFTP
class provides a method named
chdir
(short for "change directory") for this purpose. Here's how to use
chdir
:
<?php
// ...
$directory = '/path/to/remote/directory';
$sftp->chdir($directory);
<?php
// ...
echo $sftp->pwd(); // Outputs the current directory
Changing SFTP versions
SFTP has seven versions, defined from v0 to v6. OpenSSH has support only for v3, but there are SFTP servers that support multiple, or even all versions. If you are using phpseclib ≥ 3.0.11, you can set the preferred version by calling
setPreferredVersion($versionNumber)
, where
$versionNumber
is a variable holding the version as an integer. In case you want to use version 6, you have to call
setPreferredVersion(6)
. You can see what versions the server supports by calling the
getSupportedVersions()
method.
