instance-provider.php

<?php

// Here we are, in any scope imaginable. It doesn't matter which
$my_object = new My_Class();

add_filter( 'jpb.provider.my_class', function() use ( $my_object ) {
	return $my_object || new My_Class();
} );

// This is in the global scope
function get_my_class_instance() {
	$obj = apply_filters( 'jpb.provider.my_class', false );
	if( ! $obj ) {
		throw new Exception( "This is embarassing, isn't it?" );
	}
	return $obj;
}