Compact throws notice on PHP7.3 at ajax-actions.php

[pilou69]

There is no $noparents variable if the taxonomy is not hierarchical, so the compact used for the taxonomy supplemental throws a notice.

function wp_ajax_add_tag
line 1039

Before:

<?php
        $level = 0;
        if ( is_taxonomy_hierarchical( $taxonomy ) ) {
                $level = count( get_ancestors( $tag->term_id, $taxonomy, 'taxonomy' ) );
                ob_start();
                $wp_list_table->single_row( $tag, $level );
                $noparents = ob_get_clean();
        }

        ob_start();
        $wp_list_table->single_row( $tag );
        $parents = ob_get_clean();

        $x->add(
                array(
                        'what'         => 'taxonomy',
                        'supplemental' => compact( 'parents', 'noparents' ),
                )
        );

Proposed fix:

<?php
        $level = 0;
        $taxonomy_supplemental = [];
        if ( is_taxonomy_hierarchical( $taxonomy ) ) {
                $level = count( get_ancestors( $tag->term_id, $taxonomy, 'taxonomy' ) );
                ob_start();
                $wp_list_table->single_row( $tag, $level );
                $taxonomy_supplemental['noparents'] = ob_get_clean();
        }

        ob_start();
        $wp_list_table->single_row( $tag );
        $taxonomy_supplemental['parents'] = ob_get_clean();

        $x->add(
                array(
                        'what'         => 'taxonomy',
                        'supplemental' => $taxonomy_supplemental,
                )
        );

[SergeyBiryukov]

Appears to be missed in #44416.

[SergeyBiryukov]

In 45034:

Taxonomy: Initialize $noparents variable in wp_ajax_add_tag() to avoid a notice with compact() in PHP 7.3.

Props pilou69.
Fixes #46670.

[pilou69]

I should mention that the result of your fix https://core.trac.wordpress.org/changeset/45034 is not exactly what PHP7.2 did.

You see, in PHP7.2 if the variable for compact didn't exists the resulting array won't have the key with the variable name.

With Your change the 'noparents' key will be always there. I don't know if it's a mistake or You were intended to do that.