Implementing the Singleton Pattern in PHP 5

“As you probably know, in software engineering there is a set of
design patterns that are universally tested, approved and accepted
as advanced recipes for programming. One of these patterns is the
Singleton design pattern, which is based on the mathematical
concept of a singleton (a set with a single element). Part of the
well-known Gang of Four (GoF) design patterns, it calls for
restricting the instantiation of a class to one object. (Those who
are familiar with design patterns may be interested to know that
the Singleton pattern in itself is an implementation of the
Responsibility pattern.)

“Sometimes the Singleton pattern can help complete important
programming tasks, but only you can decide where and when it fits
your needs. As a pointer, the Singleton pattern fits well when you
manage a shared resource — a printer, a file manager, a database
connection, loggers, and so on — because your application should
have only a single instance in order to avoid conflicting requests
for the same resource and to minimize performance issues.

“Before deciding to use the Singleton pattern, you should first
answer “yes” to three main questions:”

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