How to deal with global information without creating a Singleton class

I am trying to walk away from the Singleton pattern when it comes to develop plugins for WordPress.

Why?

Because I have been reading in some sources (here, here, here, here …) and came up with the conclusion that they are a bad thing. Or at least, not something one should use just because.

Why would I need a Singleton-like behavior?

Because I want to have an object with properties where multiple classes along different plugins can write and read those properties.

And I sincerely do not know how to approach this.

Can you please let me know how you would do it?

There may be different cases with different solutions, so I will suppose a real example.

Example:

A plugin called “Example Form” creates a custom form on the WordPress site.

The form is processed via a method added to the init hook by the plugin class.

And while processing the form I may want to add some error or success messages to the active instance, so I can then display those messages in a theme doing somethig like:

But I don’t have access to the “original” instance because I called a satic setup method in the main plugin file.

And that is why a common solution is to make the PLUGINCLASS use the Singleton pattern, which I want to avoid.

Did I come up with my own ideas?

Yes.

I thought about: