On design patterns: When should I use the singleton?

Question

The glorified global variable - becomes a gloried global class. Some say breaking object-oriented design.

Give me scenarios, other than the good old logger where it

Answer 1

Shared resources. Especially in PHP, a database class, a template class, and a global variable depot class. All have to be shared by all modules/classes that are being used throughout the code.

It's a true object usage -> the template class contains the page template that is being built, and it gets shaped, added, changed by modules that are adding to page output. It has to be kept as a single instance so that this can happen, and the same goes for databases. With a shared database singleton, all modules' classes can get access to queries and get them without having to rerun them.

A global variable depot singleton provides you a global, reliable, and easily usable variable depot. It tidies up your code a great lot. Imagine having all configuration values in an array in a singleton like:

$gb->config['hostname']

or having all language values in an array like:

$gb->lang['ENTER_USER']

In the end of running the code for the page, you get, say, a now mature:

$template

Singleton, a $gb singleton that has the lang array for replacing into it, and all output loaded and ready. You just replace them into the keys that are now present in mature template object's page value, and then serve it out to user.

The great advantage of this is you can do ANY post-processing you like on anything. You can pipe all language values to google translate, or another translate service and get them back, and replace them into their places, translated, for example. or, you can replace in page structures, or, content strings, as you want.