PHP inline if statement always returns false

can't seem to start this working properly, any idea what could be the problem? The variable APP_NAME is equal to string 'test', if I do this if statement in a regular way it works as it should.

<?=form_radio('filter', 'y', $info['enable_categories'] == 'y' ? true : false, 'id="app" '.APP_NAME == "test" ? '' : 'disabled'.'')?>

The disabled parameter has to be put into the same last parameter as id.

But this way I get the false value even if APP_NAME equals 'test'.