Is something like the following pseudocode possible in PHP?
$backing_type='work';
$work_token='123';
$review_token='456';
echo ${$backing_type}_token;
//prints '123';
Yes. You can do the following:
echo ${$backing_type . '_token'};
However, I would consider this messy programming. Using an array would be preferred:
$arr = array('work' => 123, 'review' => 456);
echo $arr[$backing_type];