PHP程序运行的时候,既然是每一个HTTP请求对应一个数据库PDO连接对象实例,那么单例模式是否在PHP里面是否有意义呢?
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PHP程序运行的时候,既然是每一个HTTP请求对应一个数据库PDO连接对象实例,那么单例模式是否在PHP里面是否有意义呢?
PDO连接对象在每次请求中都是不同的,但是注意,这里不同的是PHP的对象,并不是实际的数据库连接。在持久模式下,虽然每次请求时都会新建新的PDO对象,但是实际上这些对象会有pdo扩展控制共享数据库的底层连接。
单例模式当然是非常有用的,在单例模式下你只需要构建一个PHP对象,且不说这些对象里的PDO是不是有底层共享实现,光单例就可以节省对象本身的内存和其他开销。
另外,这是两个概念,你不能揉在一起说,PHP的一些底层实现并不受PHP请求的生命周期控制,不能以PHP的请求周期去考量pdo扩展的实现。

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