In the attached php file (with a mform class definition method), I added a "radio" and a "filemanager" mform element.

"Filemenager" SHOULD get disabled on the basis of the selection of the radio button.
If the first "radio" is selected, the filemanager is active. Otherwise, it is not.

In spite of this, it seems the disabilitation does not ALWAYS work. Infact, for instance, it does not work if the filemanager element is added to the mform using $mform->addGroup.

You can try it by yourself coping the attached file to your local moodle root and navigating it.

It seems the line:
$mform->disabledIf($filemanagerbasename, $booleanbasename, 'neq', '1');
in line 61 has no effect.

On the opposite side: by setting

$usefilemanagergroup = false

in line 47, the same "filemanager" element is added to the form using the simpler $mform->addElement and the disabilitation works fine.