PHP与FTP：实现远程文件的加密和解密

<?php
$ftp_server = "ftp.example.com";
$ftp_username = "username";
$ftp_password = "password";

// 连接FTP服务器
$connection = ftp_connect($ftp_server);
if (!$connection) {
    die("无法连接到FTP服务器");
}

// 登录FTP服务器
$login = ftp_login($connection, $ftp_username, $ftp_password);
if (!$login) {
    die("FTP登录失败");
}

// 上传文件
$file_path = "/path/to/local/file/example.txt";
$upload = ftp_put($connection, "/path/to/remote/file/example.txt", $file_path, FTP_BINARY);
if (!$upload) {
    die("文件上传失败");
}

// 下载文件
$download = ftp_get($connection, "/path/to/local/file/example.txt", "/path/to/remote/file/example.txt", FTP_BINARY);
if (!$download) {
    die("文件下载失败");
}

// 关闭FTP连接
ftp_close($connection);
?>

<?php
// 加密文件
function encryptFile($file_path, $key) {
    $content = file_get_contents($file_path);
    $encrypted_content = openssl_encrypt($content, "AES-256-CBC", $key, 0, openssl_random_pseudo_bytes(16));
    file_put_contents($file_path, $encrypted_content);
}

// 解密文件
function decryptFile($file_path, $key) {
    $encrypted_content = file_get_contents($file_path);
    $decrypted_content = openssl_decrypt($encrypted_content, "AES-256-CBC", $key, 0, openssl_random_pseudo_bytes(16));
    file_put_contents($file_path, $decrypted_content);
}

// 使用FTP上传加密文件
$file_path = "/path/to/local/file/example.txt";
$key = "encryption_key";
encryptFile($file_path, $key);
$upload = ftp_put($connection, "/path/to/remote/file/example.txt", $file_path, FTP_BINARY);
if (!$upload) {
    die("加密文件上传失败");
}

// 使用FTP下载加密文件并解密
$download = ftp_get($connection, "/path/to/local/file/example.txt", "/path/to/remote/file/example.txt", FTP_BINARY);
if (!$download) {
    die("加密文件下载失败");
}
$file_path = "/path/to/local/file/example.txt";
decryptFile($file_path, $key);

// 关闭FTP连接
ftp_close($connection);
?>