While ldap_get_entries_moodle() PHPdocs state that it returns "array ldap-entries with lower-cased attributes as indexes.", this is not true. It uses ldap_get_attributes() internally, which returns both numerically indexed attribute names, and dictionary-like entries indexed by attribute names.

Current code lowercases the dictionary-like entries, but then uses the numerically indexed entries for the attribute names used as keys in the returned array. The numerically indexed names might or might not be lowercased, depending on the LDAP server and PHP version) version. E.g., OpenLDAP 2.x, Novell eDirectory 8.x and MS Active Directory return mixed-cased attribute names, and PHP 5.x and PHP 7.x don't lowercase them inside ldap_get_entries().

This is probably why all calls to ldap_get_entries_moodle() are followed by calls to array_change_key_case(), even if that shouldn't be necessary, according to the function's PHPdocs.

The attached patches fix the function and add some unit tests to avoid regressions in the future.

Saludos.
Iñaki.