Discussion settings: save 'closed' instead of empty string when pingback/comment checkboxes are unchecked

[chubes4]

Trac ticket

See https://core.trac.wordpress.org/ticket/51842 (related, previously closed as worksforme)

Description

When "Allow link notifications from other blogs (pingbacks and trackbacks) on new posts" is unchecked in Settings → Discussion and saved, the default_ping_status option is stored as an empty string "" instead of "closed".

This happens because options-discussion.php uses a bare checkbox:

<input name="default_ping_status" type="checkbox" id="default_ping_status" value="open" ... />

When unchecked, HTML forms don't include the field in the submission. The generic handler in options.php saves null, which update_option() stores as "":

$value = null;
if ( isset( $_POST[ $option ] ) ) {
    $value = $_POST[ $option ];
}
update_option( $option, $value );

The same issue affects default_comment_status.

Impact

• Every new post created after unchecking this setting gets ping_status = "" in the database
• The REST API schema only accepts "open" or "closed", so "" fails validation with a 400 error
• Gutenberg's Real-Time Collaboration feature (persistCRDTDoc) round-trips the full entity record through REST on page load, exposing this as a user-visible 400 error (see Gutenberg #77049 / #77050)
• MySQL strict mode configurations crash with Column 'ping_status' cannot be null (Trac #51842)

The fix

Adds a hidden input before each checkbox so that unchecking submits "closed" instead of nothing:

<input type="hidden" name="default_ping_status" value="closed" />
<input name="default_ping_status" type="checkbox" id="default_ping_status" value="open" ... />

When the checkbox is checked, its "open" value overrides the hidden input (standard HTML behavior — later inputs with the same name take precedence). When unchecked, "closed" is submitted.

This is the standard pattern used elsewhere in WordPress for checkbox options that need an explicit "off" value.

Testing instructions

1. Go to Settings → Discussion
2. Uncheck "Allow link notifications from other blogs (pingbacks and trackbacks) on new posts"
3. Uncheck "Allow people to submit comments on new posts"
4. Click Save Changes
5. Verify in the database: SELECT option_value FROM wp_options WHERE option_name IN ('default_ping_status', 'default_comment_status')
6. Before fix: Both values are "" (empty string)
7. After fix: Both values are "closed"
8. Re-check both checkboxes and save — verify values are "open"

AI Disclosure

AI assistance: Yes
Tool(s): Claude Code (claude-opus-4-6)
Used for: Tracing the root cause from a Gutenberg 400 error through nginx logs, REST API validation, and wp-admin source code. The fix pattern (hidden input before checkbox) and the specific lines to change were identified and validated by AI, then reviewed and tested on a production WordPress multisite by a human contributor.

Related

• Trac #51842 — Same root cause reported in 2020, closed as worksforme (MySQL crash symptom)
• Gutenberg #77049 — The collaboration feature that exposes this as a 400 error
• Gutenberg #77050 — Companion fix to only persist CRDT meta

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