Why was my selection of categories not properly saved ?

If a large category selection is not retained after saving, ask your webmaster to check the PHP limits actually applying to the Back Office. Two different limits can be involved:

• max_input_vars limits the number of input variables. The form includes other fields and may include several entries per element; counting categories alone is insufficient.
• post_max_size limits the total size of the POST request, expressed in bytes or using a suffix such as M. It is not a category count.

For example, max_input_vars = 3000 may suit a form containing fewer than 3,000 variables, after measuring the actual number and allowing a margin. This does not determine a corresponding post_max_size value.

Ask your webmaster to check logs, the PHP SAPI used by the Back Office and effective values after changes. CLI configuration can differ from web-server configuration. Additional hosting restrictions should be examined where present; Suhosin is not a universal requirement.

Save again, reload the page and check several categories near both ends of the selection before regenerating the feed.