比如数据库连接池就是单例设计模式的一个例子：我们一般不想让应用程序具有连接池类的多个资源密集型实例。

An example use case for a singleton would be a database connection pool: you don't want your application to have multiple resource-intensive instances of a connection pool class.

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然后展示了 PHP V5.3 的 LSB 特性，并给出了单例和活动记录设计模式。

Then it shows how PHP V5.3's LSB feature resolves those issues, while showing implementations of the singleton and active record design patterns.

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单例模式可能是最常用的OOP设计模式之一了；它限制了一个类的对象实例数只能为1。

The singleton pattern is probably one of the most often used OOP design patterns; it restricts the number of object instances of a class to one.

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