PHP fsockopen 模擬 HTTP POST/GET 請求完整指南：從 Socket 底層到封裝復用

PHP fsockopen 模擬 HTTP POST/GET 請求完整指南：從 Socket 底層到封裝復用

在無 cURL 擴展、或需精確控制 TCP 層行為（如自定義 Header、Keep-Alive、Chunked 傳輸）時，fsockopen 是 PHP 底層網路編程的核心工具。本文從原理解析、完整封裝類、異常處理到生產環境優化，全方位講解如何用 fsockopen 實現健壯的 HTTP 客戶端。

一、核心原理與協議基礎

fsockopen 建立 TCP 連接後，需手動構造符合 RFC 7230 的 HTTP 請求報文：

GET /path?query=1 HTTP/1.1\r\n
Host: example.com\r\n
User-Agent: Custom-Agent\r\n
Connection: close\r\n
\r\n

關鍵點：

• 雙 CRLF (\r\n\r\n) 分隔 Header 與 Body
• Host 頭必須（HTTP/1.1 強制）
• Content-Length 必須精確匹配 Body 字節數
• Chunked 編碼：大 Body 可分塊傳輸，結尾 0\r\n\r\n

二、生產級封裝類：SocketHttpClient

<?php
class SocketHttpClient {
    private $host;
    private $port;
    private $timeout;
    private $fp;
    private $errno;
    private $errstr;

    public function __construct(string $host, int $port = 80, float $timeout = 10.0) {
        $this->host = $host;
        $this->port = $port;
        $this->timeout = $timeout;
    }

    // 發送 GET 請求
    public function get(string $path, array $query = [], array $headers = []): string|false {
        $queryStr = http_build_query($query);
        $url = $path . ($queryStr ? '?' . $queryStr : '');
        $request = "GET $url HTTP/1.1\r\n";
        $request .= $this->buildHeaders($headers);
        $request .= "Connection: close\r\n\r\n";
        return $this->execute($request);
    }

    // 發送 POST 請求
    public function post(string $path, array $data = [], array $headers = []): string|false {
        $body = http_build_query($data);
        $request = "POST $path HTTP/1.1\r\n";
        $request .= $this->buildHeaders($headers);
        $request .= "Content-Type: application/x-www-form-urlencoded\r\n";
        $request .= "Content-Length: " . strlen($body) . "\r\n";
        $request .= "Connection: close\r\n\r\n";
        $request .= $body;
        return $this->execute($request);
    }

    // 支援 JSON POST
    public function postJson(string $path, array $data, array $headers = []): string|false {
        $body = json_encode($data);
        $request = "POST $path HTTP/1.1\r\n";
        $request .= $this->buildHeaders($headers);
        $request .= "Content-Type: application/json\r\n";
        $request .= "Content-Length: " . strlen($body) . "\r\n";
        $request .= "Connection: close\r\n\r\n";
        $request .= $body;
        return $this->execute($request);
    }

    private function buildHeaders(array $headers): string {
        $default = [
            'Host' => $this->host,
            'User-Agent' => 'PHP-SocketHttpClient/1.0',
            'Accept' => '*/*',
        ];
        $merged = $default + $headers;
        $str = '';
        foreach ($merged as $k => $v) {
            $str .= "$k: $v\r\n";
        }
        return $str;
    }

    private function execute(string $request): string|false {
        $this->fp = @fsockopen($this->host, $this->port, $this->errno, $this->errstr, $this->timeout);
        if (!$this->fp) {
            error_log("fsockopen failed: [$this->errno] $this->errstr");
            return false;
        }
        stream_set_timeout($this->fp, (int)$this->timeout, (int)(($this->timeout - (int)$this->timeout) * 1e6));
        fwrite($this->fp, $request);

        $response = '';
        $info = stream_get_meta_data($this->fp);
        while (!feof($this->fp) && !$info['timed_out']) {
            $response .= fread($this->fp, 8192);
            $info = stream_get_meta_data($this->fp);
        }
        fclose($this->fp);

        if ($info['timed_out']) {
            error_log("Socket timeout reading from {$this->host}:{$this->port}");
            return false;
        }
        return $response;
    }

    // 解析響應：分離 Header 與 Body
    public static function parseResponse(string $response): array {
        list($headerBlock, $body) = explode("\r\n\r\n", $response, 2) + ['', ''];
        $headers = [];
        foreach (explode("\r\n", $headerBlock) as $line) {
            if (strpos($line, ':') !== false) {
                [$k, $v] = explode(':', $line, 2);
                $headers[trim($k)] = trim($v);
            }
        }
        // 處理 Chunked 編碼
        if (isset($headers['Transfer-Encoding']) && stripos($headers['Transfer-Encoding'], 'chunked') !== false) {
            $body = self::decodeChunked($body);
        }
        return ['headers' => $headers, 'body' => $body, 'status' => $headers['Status'] ?? ''];
    }

    private static function decodeChunked(string $data): string {
        $result = '';
        $pos = 0;
        while ($pos < strlen($data)) {
            $lineEnd = strpos($data, "\r\n", $pos);
            if ($lineEnd === false) break;
            $length = hexdec(trim(substr($data, $pos, $lineEnd - $pos)));
            if ($length === 0) break;
            $pos = $lineEnd + 2;
            $result .= substr($data, $pos, $length);
            $pos += $length + 2; // skip \r\n
        }
        return $result;
    }
}

// 使用示例
$client = new SocketHttpClient('api.example.com', 443, 15); // HTTPS 需配合 SSL 上下文
// 註：fsockopen 直連 HTTPS 需 ssl:// 前綴與 stream_context_create
// 見下文「HTTPS 支援」章節

三、HTTPS 支援：SSL/TLS 封裝

// 修改構造函數或連接邏輯
$host = 'ssl://api.example.com'; // 或 'tls://'
$port = 443;
$context = stream_context_create([
    'ssl' => [
        'verify_peer' => true,
        'verify_peer_name' => true,
        'cafile' => '/etc/ssl/certs/ca-certificates.crt',
    ]
]);
$this->fp = @stream_socket_client(
    "$host:$port",
    $this->errno,
    $this->errstr,
    $this->timeout,
    STREAM_CLIENT_CONNECT,
    $context
);

注意：fsockopen 不直接支援 SSL 參數，必須用 stream_socket_client + stream_context_create。

四、異常處理與健壯性增強

五、效能優化與最佳實踐

1. 連接復用：移除 Connection: close，實現 Keep-Alive（需手動管理連接池）
2. 非阻塞 I/O：stream_set_blocking($fp, 0) + stream_select 實現高併發
3. 流式處理大響應：邊讀邊處理，避免大 Body 佔用記憶體
4. DNS 緩存：生產環境建議用 gethostbyname 預解析並緩存 IP

六、何時選擇 fsockopen vs cURL

總結：fsockopen 是理解 HTTP 協議、排查網路疑難雜症、特殊環境下的利器。但常規業務開發強烈建議使用 cURL 或 Guzzle 等成熟庫，僅在底層調試、無擴展環境、自定義協議時直接操作 Socket。