php 多个mysql连接数据库连接池

class ConnectionPool {
    private $pool = [];
    private $minConnections;
    private $maxConnections;
    private $connectionString;

    public function __construct($connectionString, $minConnections = 5, $maxConnections = 10) {
        $this->connectionString = $connectionString;
        $this->minConnections = $minConnections;
        $this->maxConnections = $maxConnections;
        $this->initializePool();
    }

    private function initializePool() {
        for ($i = 0; $i < $this->minConnections; $i++) {
            $this->pool[] = $this->createConnection();
        }
    }

    private function createConnection() {
        try {
            return new PDO($this->connectionString);
        } catch (PDOException $e) {
            // 处理异常
        }
    }

    public function getConnection() {
        if (empty($this->pool)) {
            if (count($this->pool) < $this->maxConnections) {
                $this->pool[] = $this->createConnection();
            } else {
                // 等待连接释放
                // 这里可以实现等待逻辑，例如使用信号量或条件变量
            }
        }
        return array_pop($this->pool);
    }

    public function releaseConnection(PDO $connection) {
        $this->pool[] = $connection;
    }
}

// 使用示例
$pool = new ConnectionPool('mysql:host=localhost;dbname=testdb', 5, 10);
$dbConnection = $pool->getConnection();
// 执行数据库操作...
$pool->releaseConnection($dbConnection);