Callable Arrays in PHP since 7.0

I noticed that since PHP 7.0, I can use syntax like this:

<?php

["a", "b"]();

When I run it, I encounter the following error:

Fatal error: Uncaught Error: Class 'a' not found in ...

It seems that the PHP interpreter tries to resolve [“a”, “b”] as a reference to a class a with a method b and attempts to invoke it.

• Why does PHP interpret this array in this way?
• What is the underlying mechanism behind this behavior?
• Is there any official documentation or resources that explain this feature?