Callable

In Mustache.php, a variable is considered "callable" if the variable is:

1. an anonymous function.
2. an instance of a class which implements __invoke.

strict_callables

The Mustache Engine accepts a strict_callables option, which defaults to true as of v3.0.0. If set to false, Mustache will also following as "callable":

1. an object and the name of a public function, e.g. [$someObject, 'methodName'].
2. a class name and the name of a public static function, e.g. ['SomeClass', 'methodName'].

Disabling strict_callables is not recommended.