PHP FTP 進階：非阻塞下載、檔案刪除、大小獲取完整實例

非阻塞下載（支援大檔案/進度條）

function ftp_nb_download(string $host, string $user, string $pass, string $remote, string $local, callable $progress = null): bool {
    $conn = ftp_connect($host) or die("連接失敗");
    ftp_login($conn, $user, $pass) or die("登入失敗");
    ftp_pasv($conn, true);
    
    $localHandle = fopen($local, 'w') or die("無法建立本地檔案");
    $ret = ftp_nb_fget($conn, $localHandle, $remote, FTP_BINARY, 0);
    
    while ($ret === FTP_MOREDATA) {
        if ($progress) {
            $progress(ftell($localHandle), ftp_size($conn, $remote));
        }
        $ret = ftp_nb_continue($conn);
    }
    
    fclose($localHandle);
    ftp_close($conn);
    
    if ($ret !== FTP_FINISHED) {
        unlink($local);
        return false;
    }
    return true;
}

// 使用：顯示進度
ftp_nb_download('ftp.example.com', 'u', 'p', 'big.iso', 'big.iso', function($downloaded, $total) {
    $pct = $total ? round($downloaded/$total*100, 1) : '?';
    echo "\r已下載: $downloaded / $total ($pct%)";
});

刪除遠端檔案

function ftp_delete_file(string $host, string $user, string $pass, string $remote): bool {
    $conn = ftp_connect($host) or return false;
    ftp_login($conn, $user, $pass) or return false;
    $ok = @ftp_delete($conn, $remote);
    ftp_close($conn);
    return $ok;
}

獲取遠端檔案大小

function ftp_remote_size(string $host, string $user, string $pass, string $remote): ?int {
    $conn = ftp_connect($host) or return null;
    ftp_login($conn, $user, $pass) or return null;
    $size = ftp_size($conn, $remote); // -1 表示失敗或非檔案
    ftp_close($conn);
    return $size >= 0 ? $size : null;
}

批次操作封裝類

class FtpClient {
    private $conn;
    
    public function __construct(string $host, string $user, string $pass, int $port = 21, bool $pasv = true) {
        $this->conn = ftp_connect($host, $port, 30);
        if (!$this->conn || !ftp_login($this->conn, $user, $pass)) {
            throw new Exception("FTP 連接/登入失敗");
        }
        ftp_pasv($this->conn, $pasv);
    }
    
    public function download(string $remote, string $local, callable $progress = null): bool { /* ... */ }
    public function upload(string $local, string $remote): bool { /* ftp_put / ftp_nb_fput */ }
    public function delete(string $remote): bool { return @ftp_delete($this->conn, $remote); }
    public function size(string $remote): ?int { $s = ftp_size($this->conn, $remote); return $s>=0?$s:null; }
    public function list(string $dir = '.'): array { return ftp_nlist($this->conn, $dir); }
    public function __destruct() { if ($this->conn) ftp_close($this->conn); }
}

安全建議

• 生產環境改用 SFTP (SSH2) 或 FTPS，避免明文傳輸密碼與數據。
• PHP 可用 phpseclib/Net_SFTP 純 PHP 實現，無需 ssh2 擴展。
• 限制 FTP 用戶權限：chroot 至特定目錄，唯讀/寫入分離帳號。