Hide charset setting for new installs

[nacin]

If your site is set to UTF-8, we should hide the blog_charset setting field. There is no reason to change it away from UTF-8, and doing so can break your content and possibly make your site insecure.

This won't prevent it from changing via options.php — just hiding the primary UI.

We need to keep in mind that "UTF-8" comes in a few forms, both with and without hyphens (also, case insensitivity). We will need to check those.

Technically, this means we've removed an option from WordPress, so I reserve the right to add back one. :-)

[nacin]

In [21467]:

Hide the charset setting for installs that have a charset of UTF-8 already. fixes #21507.

[SergeyBiryukov]

[21467] introduced a bug: if you go to Reading Settings and click Save Changes, the charset gets overwritten with an empty string in wp-admin/options.php (since it's still in $whitelist_options):
​http://core.trac.wordpress.org/browser/tags/3.4.1/wp-admin/options.php#L137

As far as I can see, there's no way to output arbitrary hidden fields using the Settings API.

21507.patch​ moves the check to the beginning of the form and adds hidden blog_charset field right after settings_fields() if the charset is UTF-8.

[nacin]

In [21539]:

Output a hidden input of blog_charset when we are hiding the option. props SergeyBiryukov. see #21507.

[SergeyBiryukov]

With PHPDocs

[nacin]

In [21653]:

Remove reference to blog_charset option in Settings > Reading help. fixes #21507.

[nacin]

I think I'd rather avoid the hidden input with 21507.diff​.

This also protects the option from being changed in multisite (as well it should be), forcing any single-site changes to go through options.php.

[nacin]

In [21842]:

Avoid the need for a hidden input when suppressing the blog_charset option. fixes #21507.