add_settings_section and add_settings_field callback param should be of 'callable' type

[aidanlane]

Currently the type is string, which is inaccurate and will be flagged as such by tools such as Scrutinizer (​https://scrutinizer-ci.com/).

add_settings_section:
https://core.trac.wordpress.org/browser/trunk/src/wp-admin/includes/template.php#L1191

add_settings_field:
https://core.trac.wordpress.org/browser/trunk/src/wp-admin/includes/template.php#L1229

callable is the type is used by add_action (​https://developer.wordpress.org/reference/functions/add_action/), add_filter (​https://developer.wordpress.org/reference/functions/add_filter` and by many other functions already 34032.

Refs:
​http://uk1.php.net/manual/en/language.types.callable.php
​https://github.com/phpDocumentor/fig-standards/blob/master/proposed/phpdoc.md#keyword
​http://www.phpdoc.org/docs/latest/guides/types.html

[DrewAPicture]

Hi @aidanlane, nice catch and thanks for the patch!

[DrewAPicture]

In 36642:

Docs: Update the type for $callback parameters to callable in DocBlocks for add_settings_section() and add_settings_field().

Props aidanlane.
Fixes #35772.

[aidanlane]

Fantastic, thanks @DrewAPicture!