How do I save custom options on the options page ‘Reading’?

Found it; One needs to use a so-called ‘whitelisted’ group:

register_setting("reading", "honeycomb-reading-share");

Existing option-pages seem to all have a group-name that corrsponds to their page-name.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)