PHP 및 FTP: 원격 파일의 차등 및 증분 백업 구현

<?php
function downloadFile($remoteFile, $localFile)
{
    $ftpServer = "ftp.example.com";
    $ftpUsername = "username";
    $ftpPassword = "password";
    
    $ftpConn = ftp_connect($ftpServer);
    ftp_login($ftpConn, $ftpUsername, $ftpPassword);
    
    $localFileSize = file_exists($localFile) ? filesize($localFile) : 0;
    $ftpFileSize = ftp_size($ftpConn, $remoteFile);
    
    if ($localFileSize !== $ftpFileSize) {
        if (ftp_get($ftpConn, $localFile, $remoteFile, FTP_BINARY)) {
            echo "文件下载成功！";
        } else {
            echo "文件下载失败！";
        }
    } else {
        echo "本地文件与远程文件一致，无需下载！";
    }
    
    ftp_close($ftpConn);
}

// 调用示例
downloadFile("/remote/path/file.txt", "/local/path/file.txt");
?>

<?php
function uploadFile($localFile, $remoteFile)
{
    $ftpServer = "ftp.example.com";
    $ftpUsername = "username";
    $ftpPassword = "password";
    
    $ftpConn = ftp_connect($ftpServer);
    ftp_login($ftpConn, $ftpUsername, $ftpPassword);
    
    $remoteFileSize = ftp_size($ftpConn, $remoteFile);
    $localFileSize = filesize($localFile);
    
    if ($remoteFileSize !== $localFileSize) {
        if (ftp_put($ftpConn, $remoteFile, $localFile, FTP_BINARY)) {
            echo "文件上传成功！";
        } else {
            echo "文件上传失败！";
        }
    } else {
        echo "远程文件与本地文件一致，无需上传！";
    }
    
    ftp_close($ftpConn);
}

// 调用示例
uploadFile("/local/path/file.txt", "/remote/path/file.txt");
?>