PHP Memcached 快取操作類別完整實作

前置需求

• 伺服器安裝 Memcached 服務：yum install memcached 或 apt-get install memcached
• PHP 安裝 memcached 擴充套件（非 memcache）：pecl install memcached
• 啟用擴充：extension=memcached.so

快取介面定義

interface CacheInterface {
    public function set($key, $value, $expire = 0);
    public function get($key);
    public function delete($key);
    public function flush();
}

Memcached 實作類別

class MemcachedCache implements CacheInterface {
    private $memcached;
    private $servers = []; // 多伺服器支援
    private $defaultServer = 0;
    
    public function __construct(array $config = []) {
        if (!class_exists('Memcached')) {
            throw new Exception('Memcached 擴充套件未安裝');
        }
        
        $this->memcached = new Memcached();
        
        // 預設配置
        $defaultConfig = [
            'servers' => [
                ['host' => '127.0.0.1', 'port' => 11211, 'weight' => 100]
            ],
            'options' => [
                Memcached::OPT_COMPRESSION => true,
                Memcached::OPT_LIBKETAMA_COMPATIBLE => true, // 一致性雜湊
                Memcached::OPT_BINARY_PROTOCOL => true,
            ]
        ];
        
        $config = array_merge_recursive($defaultConfig, $config);
        $this->servers = $config['servers'];
        
        // 設定選項
        foreach ($config['options'] as $opt => $val) {
            $this->memcached->setOption($opt, $val);
        }
        
        $this->connect();
    }
    
    private function connect() {
        $serverList = [];
        foreach ($this->servers as $s) {
            $serverList[] = [$s['host'], $s['port'], $s['weight'] ?? 100];
        }
        $this->memcached->addServers($serverList);
    }
    
    public function set($key, $value, $expire = 0) {
        // 自動序列化複雜資料
        $flags = is_scalar($value) ? 0 : Memcached::SERIALIZER_PHP;
        return $this->memcached->set($key, $value, $expire, $flags);
    }
    
    public function get($key) {
        return $this->memcached->get($key);
    }
    
    public function delete($key) {
        return $this->memcached->delete($key);
    }
    
    public function flush() {
        return $this->memcached->flush();
    }
    
    // 進階功能
    public function getMulti(array $keys) {
        return $this->memcached->getMulti($keys);
    }
    
    public function increment($key, $offset = 1, $initial = 0, $expire = 0) {
        return $this->memcached->increment($key, $offset, $initial, $expire);
    }
    
    public function getStats() {
        return $this->memcached->getStats();
    }
}

使用範例

// 初始化（可從配置檔讀取）
$cache = new MemcachedCache([
    'servers' => [
        ['host' => '10.0.0.1', 'port' => 11211],
        ['host' => '10.0.0.2', 'port' => 11211],
    ]
]);

// 基本操作
$cache->set('user:1001', ['name' => '張三', 'email' => 'zhang@example.com'], 3600);
$user = $cache->get('user:1001');

// 計數器（原子操作）
$cache->set('page_views', 0);
$views = $cache->increment('page_views'); // 1, 2, 3...

// 批量讀取
$profiles = $cache->getMulti(['user:1001', 'user:1002', 'user:1003']);

// 監控統計
$stats = $cache->getStats();
print_r($stats);

關鍵優化建議

1. 鍵名規範：使用前綴分隔業務域（如 user:, session:, api:）
2. 序列化選擇：預設 PHP 序列化相容性佳，效能敏感場景可改用 igbinary 或 msgpack
3. 壓縮策略：大數據（>1KB）啟用壓縮 OPT_COMPRESSION
4. 一致性雜湊：多伺服器必須啟用 OPT_LIBKETAMA_COMPATIBLE 避免節點變動導致大量失效
5. 連線池：長連線減少握手開銷，PHP-FPM 工作進程間自動共享