Recent Posts widget breaks ob stack

[m_i_n]

Please have a look at the following part of "Recent Posts" widget code (default-widgets.php, from line 731):

if ( ! $this->is_preview() ) {
	$cache[ $args['widget_id'] ] = ob_get_flush();
	wp_cache_set( 'widget_recent_posts', $cache, 'widget' );
} else {
	ob_flush();
}

If you're not in is_preview(), output buffer is returned to var, flushed, and turns output buffering off (it's OK). However, in other case, buffer in not returned to var, flushed (it's OK until now), but output buffering is not turned off (it should be ob_end_flush instead of ob_flush). It breaks ob stack.

The bug is noticeable in Appearance / Customize, if a theme uses output buffering on the dynamic_sidebar() function, and the widget is active.

[ocean90]

Hello m_i_n, thanks for the report.

From the PHP docs:

• ob_get_flush: Flush the output buffer, return it as a string and turn off output buffering
• ob_flush: Flush (send) the output buffer
• ob_end_flush: Flush (send) the output buffer and turn off output buffering

So I agree, we should use ob_end_flush() here.

[ocean90]

Introduced in [27966].

[westonruter]

Replying to ocean90:

So I agree, we should use ob_end_flush() here.

+1

[ocean90]

In 28195:

Recent Posts Widget: Use ob_end_flush() instead of ob_flush().

ob_end_flush() flushes the output buffer *and* turns output buffering off, same as ob_get_flush().

props m_i_n.
see #28009 for trunk.

[nacin]

In 28196:

Recent Posts Widget: Use ob_end_flush() instead of ob_flush().

Merges [28195] to the 3.9 branch.

props m_i_n.
fixes #28009.