CREATE TABLE locks (
  lock_name VARCHAR(255) NOT NULL PRIMARY KEY,
  expiry_timestamp TIMESTAMP NOT NULL,
  process_id INT NOT NULL
);

public function acquireLock(string $lockName): bool
{
    $expiryTimestamp = date('Y-m-d H:i:s', time()   $this->lockTimeout);
    $processId = getmypid();

    try {
        $this->db->query('BEGIN TRANSACTION');
        $query = $this->db->prepare(
            'INSERT INTO locks (lock_name, expiry_timestamp, process_id) VALUES (?, ?, ?, ?)'
        );
        $query->execute([$lockName, $expiryTimestamp, $processId]);

        if ($query->rowCount() > 0) {
            $this->db->commit();
            return true;
        } else {
            $this->db->rollBack();
            return false;
        }
    } catch (PDOException $e) {
        $this->db->rollBack();
        throw $e;
    }
}

public function releaseLock(string $lockName): void
{
    $processId = getmypid();

    try {
        $this->db->query('BEGIN TRANSACTION');
        $query = $this->db->prepare('DELETE FROM locks WHERE lock_name = ? AND process_id = ?');
        $query->execute([$lockName, $processId]);
        $this->db->commit();
    } catch (PDOException $e) {
        $this->db->rollBack();
        throw $e;
    }
}

use my\LockManager;

$lockManager = new LockManager();

// 获取锁
if ($lockManager->acquireLock('cart')) {
    // 修改购物车内容
    ...

    // 释放锁
    $lockManager->releaseLock('cart');
} else {
    // 重新测试或显示错误消息
}