在PHP中实现高效的数据库操作涉及到多个方面，包括数据库设计、索引、SQL优化、PHP代码优化以及使用合适的数据库抽象层等。以下是一些建议：

1. **数据库设计**：
- 使用正确的表结构和数据类型。
- 确保表中有合适的索引。
- 避免使用不必要的复杂关联。

2. **SQL优化**：
- 使用分析工具（如EXPLAIN）来检查SQL语句的执行计划。
- 避免使用SELECT *，而是明确指定需要的列。
- 使用索引覆盖（Index-covered queries）来减少数据扫描。
- 避免使用子查询，或者将子查询转换为 join。
- 使用 LIMIT 来限制返回的数据量。

3. **PHP代码优化**：
- 使用预处理语句（PDO或MySQLi）来防止SQL注入。
- 尽量减少数据库的往返次数。
- 使用缓存机制，如Redis或Memcached。
- 避免使用不必要的函数调用和计算。

4. **使用数据库抽象层**：
- 使用ORM（对象关系映射）工具，如Doctrine、Eloquent或CodeIgniter。
- 使用数据库连接池，如PdoPool或Amp\Dba。

5. **其他技巧**：
- 使用数据库特有的功能，如MySQL的```````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````