Investigate the usages and results of in_array in currently supported php versions.
During a review of
MDL-70967, it was identified that in_array throws up false +ves/-ves. It was suggested to review it's usages and confirm there are no hidden cases where this is failing and not being picked up. Refer to this comment
Note: I've only included enrolments and 3.11 but this should be a core-wide check.