In this new tutorial from PHPit.net today, Dennis Pallett talks about using globals in PHP, desscribing what they are and how to use them.
Whenever you're developing a new large-scale PHP script, you're bound to use global variables, since some data needs to be used by multiple parts of your script. Good examples of global data are script settings, database connections, user credentials and more. There are many ways of making this data global, but the most commonly used way is to use the global keyword, which we will explore later on in this article.
It's good that he mentions right from the start that most global data is a bad idea, and can really start to clutter up an application. He does help the reader prevent this, though, through the use of a few handy techniques (and design patterns).
He looks first at the "global" keyword and its use, followed by three reasons that it's not all that favorable to use. He gives other options for the "just make it global" thinking, including passing the values in function calls, passing by reference, and using the Singleton and Registry patterns to contain things a bit more. He even includes a wrapper for the registry to handle the only other globals left - the superglobals - with the same registry functionality.