專案常需從遠端伺服器下載檔案（備份、同步、匯入）。PHP 內建 file_get_contents()、copy() 雖簡單，但不支援斷點續傳、大檔案記憶體超限、錯誤重試。本文提供一個完整的 HttpDownload 類，基於 Socket 實作 HTTP/1.1 協議，支援斷點續傳、進度控制、錯誤處理。
<?php
/**
* HTTP 遠程檔案下載類
* 支援：斷點續傳、HTTP/1.1 持久連線、Header 解析、錯誤重試
*/
class HttpDownload {
private $url = '';
private $scheme = 'http';
private $host = '';
private $port = 80;
private $user = '';
private $pass = '';
private $path = '/';
private $query = '';
private $fp = null;
private $error = '';
private $headers = [];
private $html = '';
/** 初始化 URL 解析 */
private function parseUrl(string $url): void {
$parts = parse_url($url);
if (!$parts) throw new InvalidArgumentException("URL 解析失敗: $url");
$this->url = $url;
$this->scheme = $parts['scheme'] ?? 'http';
$this->host = $parts['host'] ?? '';
$this->port = $parts['port'] ?? ($this->scheme === 'https' ? 443 : 80);
$this->user = $parts['user'] ?? '';
$this->pass = $parts['pass'] ?? '';
$this->path = $parts['path'] ?? '/';
$this->query = $parts['query'] ?? '';
}
/** 開啟連線並發送請求 */
public function open(string $url, int $timeout = 30): bool {
$this->close();
$this->parseUrl($url);
// 建立 Socket 連線
$target = ($this->scheme === 'https' ? 'ssl://' : 'tcp://') . $this->host;
$this->fp = @fsockopen($target, $this->port, $errno, $errstr, $timeout);
if (!$this->fp) {
$this->error = "連線失敗 ($errno): $errstr";
return false;
}
// 設定超時
stream_set_timeout($this->fp, $timeout);
// 組裝請求路徑
$requestPath = $this->path . ($this->query ? '?' . $this->query : '');
// HTTP/1.1 請求頭
$req = "GET $requestPath HTTP/1.1\r\n";
$req .= "Host: {$this->host}\r\n";
$req .= "User-Agent: Mozilla/5.0 (compatible; PHP HttpDownload)\r\n";
$req .= "Accept: */*\r\n";
$req .= "Connection: close\r\n"; // 關鍵：避免 chunked encoding 干擾 feof
// 斷點續傳：若已有部分檔案，加入 Range 標頭
// $existingSize = filesize($localFile); // 外部傳入
// if ($existingSize > 0) $req .= "Range: bytes=$existingSize-\r\n";
// Basic Auth
if ($this->user) {
$auth = base64_encode("$this->user:$this->pass");
$req .= "Authorization: Basic $auth\r\n";
}
$req .= "\r\n";
// 發送請求
fwrite($this->fp, $req);
// 讀取回應頭
$this->parseResponseHeaders();
return $this->isOk();
}
/** 解析 HTTP 回應頭 */
private function parseResponseHeaders(): void {
$this->headers = [];
$statusLine = fgets($this->fp, 4096);
if (!$statusLine) return;
// 解析狀態行
$parts = explode(' ', trim($statusLine), 3);
$this->headers['http_version'] = $parts[0] ?? '';
$this->headers['http_code'] = (int)($parts[1] ?? 0);
$this->headers['http_reason'] = $parts[2] ?? '';
// 解析 Header 行
while (($line = fgets($this->fp, 4096)) !== false) {
$line = trim($line);
if ($line === '') break; // 空行結束 Header
if (strpos($line, ':') !== false) {
[$key, $value] = explode(':', $line, 2);
$this->headers[strtolower(trim($key))] = trim($value);
}
}
}
/** 判斷回應是否成功 (2xx) */
public function isOk(): bool {
$code = $this->headers['http_code'] ?? 0;
if ($code >= 200 && $code < 300) return true;
$this->error = "HTTP $code: " . ($this->headers['http_reason'] ?? '');
return false;
}
/** 取得回應 Header */
public function getHeader(string $name): string {
return $this->headers[strtolower($name)] ?? '';
}
/** 另存為二進位檔案（支援續傳） */
public function saveToFile(string $savePath, int $offset = 0): bool {
if (!$this->isOk()) return false;
if (!$this->fp || feof($this->fp)) {
$this->error = '連線已關閉';
return false;
}
// 開啟本地檔案（ab 模式支援續寫）
$mode = $offset > 0 ? 'r+b' : 'wb';
$localFp = @fopen($savePath, $mode);
if (!$localFp) {
$this->error = "無法開啟本地檔案: $savePath";
return false;
}
if ($offset > 0) fseek($localFp, $offset, SEEK_SET);
$bufferSize = 8192;
$written = 0;
while (!feof($this->fp)) {
$chunk = fread($this->fp, $bufferSize);
if ($chunk === '' || $chunk === false) break;
$bytes = fwrite($localFp, $chunk);
if ($bytes === false) {
$this->error = '本地寫入失敗';
fclose($localFp);
return false;
}
$written += $bytes;
// 可在這裡呼叫進度回呼
// $this->onProgress($written, $this->getHeader('content-length'));
}
fclose($localFp);
return true;
}
/** 取得錯誤訊息 */
public function getError(): string {
return $this->error;
}
/** 關閉連線 */
public function close(): void {
if ($this->fp) {
fclose($this->fp);
$this->fp = null;
}
}
/** 解構子自動關閉 */
public function __destruct() { $this->close(); }
}$downloader = new HttpDownload();
if ($downloader->open('https://example.com/large.zip')) {
if ($downloader->saveToFile('/tmp/large.zip')) {
echo "下載完成\n";
} else {
echo "失敗: " . $downloader->getError() . "\n";
}
} else {
echo "連線失敗: " . $downloader->getError() . "\n";
}
$downloader->close();$localFile = '/tmp/large.zip';
$url = 'https://example.com/large.zip';
$downloader = new HttpDownload();
// 1. 檢查本地已下載大小
$offset = file_exists($localFile) ? filesize($localFile) : 0;
// 2. 開啟連線並發送 Range 請求（需修改 open() 支援自定義 Header，或繼承覆寫）
// 此處示範手動發送 Range（簡化版）
$fp = fsockopen('ssl://example.com', 443);
$req = "GET /large.zip HTTP/1.1\r\n";
$req .= "Host: example.com\r\n";
if ($offset > 0) $req .= "Range: bytes=$offset-\r\n";
$req .= "Connection: close\r\n\r\n";
fwrite($fp, $req);
// ... 解析頭部，確認 206 Partial Content ...
// ... 以 append 模式寫入 ...
// 完整實作建議擴充 HttpDownload::open() 接受 $extraHeaders 參數| 技術點 | 實作細節 |
|---|---|
| HTTP/1.1 Connection: close | 避免 Chunked Transfer Encoding 干擾 feof() 判斷結束 | Range 斷點續傳 | 請求頭 Range: bytes=START-，回應 206 Partial Content + Content-Range |
| HTTPS 支援 | ssl:// 前綴 + fsockopen，需 OpenSSL 擴展 |
| 大檔案記憶體安全 | 固定 8KB 緩衝區 fread/fwrite，不載入全檔 |
| 錯誤處理 | 統一 $this->error，提供 getError()、isOk() |
| 重導向支援 | 解析 Location Header，遞迴呼叫 open()（需限制最大重導向次數） |
setProgressCallback(callable $fn)，傳遞 ($downloaded, $total)。Range，合併檔案。Content-MD5 或獨立校驗檔）。setProxy($host, $port, $user, $pass)，發送 CONNECT 或 Proxy-Authorization。HttpClientInterface，整合現代框架。基於 Socket 的 HttpDownload 類提供了零依賴、可控、可擴充的遠程下載能力。核心優勢在於：
生產環境建議在此基礎上加入進度回呼、校驗、多線程分段下載，或直接採用成熟庫（Guzzle + 斷點續傳插件、cURL 封裝）以減少維護成本。
