Bug Report: “Undefined variable $output” PHP warning in [su_feed] shortcode

Bug Report: “Undefined variable $output” PHP warning in [su_feed] shortcode

Plugin: Shortcodes Ultimate (shortcodes-ultimate)
Version: 7.8.4 (latest as of 2026-08-19)
WordPress: 7.0.4
PHP: 8.5.4
Status: Active Summary

Using the [su_feed] shortcode on a page emits a PHP warning on every render:

PHP Warning: Undefined variable $output in
.../shortcodes-ultimate/includes/shortcodes/feed.php on line 83

The shortcode still outputs the feed correctly — this is a log-noise warning,
not a visible break — but it fires on every page load that includes feed items,
which quickly floods the PHP-FPM/nginx error log. Steps to reproduce

1. Install Shortcodes Ultimate 7.8.4 on WordPress 7.0.4 with PHP 8.x.
2. Add a page containing a feed shortcode with items available, e.g.:

[su_feed url=”https://example.com/category/news/feed/” limit=”-1″]

(Also reproduced with limit=”3″. The site uses the compatibility prefix
option “su_”, so the tag is [su_feed].)

Load the page. The warning is emitted once per shortcode render. Root cause

In includes/shortcodes/feed.php, the variable $output is used with the
concatenating assignment operator inside the foreach loop, but is never
initialized before the loop:

foreach ( $items as $item ) {

    $output .= sprintf(
        '<li><a href="%s" target="_%s" title="%s">%s</a></li>',
        esc_url( $item->get_permalink() ),
        sanitize_key( $atts['target'] ),
        esc_attr( $item->get_description() ),
        wp_kses_post( $item->get_title() )
    );

}

return sprintf(
    '<ul class="su-feed%s">%s</ul>',
    esc_attr( su_get_css_class( $atts ) ),
    $output
);

On the first loop iteration, $output is undefined, so PHP 8 emits
“Undefined variable $output”. (PHP reports the warning at the line where the
sprintf argument list ends — line 83 in 7.8.4 — which made it slightly
confusing to track down at first.) Suggested fix (one line)

Initialize $output before the loop:

$output = '';

foreach ( $items as $item ) {
    ...

(If the early-return guard “if ( ! count( $items ) )” were ever removed, the
same initialization would also protect the return statement below the loop.) Workaround

For anyone hitting this before the fix ships: a must-use plugin that
re-registers the “feed” shortcode with a corrected callback (remove_shortcode +
add_shortcode on init, priority 50 — after SU registers at priority 40)
removes the warning without modifying plugin files.

Notes

• Warning is cosmetic: feed HTML output is correct.
• Occurs on PHP 8.x; will also affect PHP 9 when release notes inevitably
  promote undefined-variable notices to errors (PHP 8.0+ already emits the
  warning under error_reporting(E_ALL)).
• Only affects the free “feed” shortcode; other shortcodes were not checked
  for the same pattern.

• This topic was modified 2 weeks, 3 days ago by Hayward.