[wp-trac] [WordPress Trac] #59818: [PHP 8.1] deprecated null in `explode()` for 'ping_sites' in `wp-admin/options-writing.php` with "Discourage search engines" on

[WordPress Trac]

#59818: [PHP 8.1] deprecated null in `explode()` for 'ping_sites' in `wp-admin
/options-writing.php` with "Discourage search engines" on
-----------------------------+--------------------------------
 Reporter:  kitchin          |       Owner:  SergeyBiryukov
     Type:  defect (bug)     |      Status:  accepted
 Priority:  normal           |   Milestone:  6.5
Component:  Administration   |     Version:
 Severity:  normal           |  Resolution:
 Keywords:  php81 has-patch  |     Focuses:  php-compatibility
-----------------------------+--------------------------------

Comment (by devmuhib):

 Can you add the testing instruction please?

 Replying to [comment:4 kitchin]:
 > Thanks for the quick action! I have a different approach that addresses
 the underling issue.
 >
 > The controller `wp-admin/options.php` uses `update_option()`
 unconditionally on all relevant elements of `$allowed_options`, even if
 they don't appear in `$_POST`. Luckily in the current codebase, or as part
 of  its design, there is a filter on `get_option( 'ping_sites' )`, called
 `privacy_ping_filter()`, which checks:
 > {{{
 > if ( '1' === get_option( 'blog_public' ) ) {
 >       return $sites;
 > } else {
 >       return '';
 > }
 > }}}
 >
 > So when `update_option()` uses `get_option()` to compare `$value` to
 `$old_value`, it sees `'' === ''`, where `explode( "\n", $value )` has
 cast `NULL` to `''`. Thus no data loss.
 >
 > My first patch mods `$allowed_options`. It does it directly, rather than
 using the filter, since the variable is very specific to the file it is
 in. Might as well make it easy to read. This patch is tested as far as
 updating options goes.
 >
 > My alternate patch also reconciles the strictness and specificity of the
 evaluation of 'blog_public' across the codebase, except multisite. In
 other words, `'1' ===` vs. `'0' != `, etc. It also makes the filter
 signature in `wp-includes/functions.php` correct. Multisite seems to have
 its own way of doing things. This patch is not tested.

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Ticket URL: <https://core.trac.wordpress.org/ticket/59818#comment:5>
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