Undefined Offset -1 in wp-includes/rewrite.php on lines 379 and 381

[thomstark]

This is what's currently in the function wp_resolve_numeric_slug_conflicts():

<?php
    $permastructs   = array_values( array_filter( explode( '/', get_option( 'permalink_structure' ) ) ) );
    $postname_index = array_search( '%postname%', $permastructs );
    if ( false === $postname_index ) {
        return $query_vars;
    }
    $compare = '';
    if ( 0 === $postname_index && ( isset( $query_vars['year'] ) || isset( $query_vars['monthnum'] ) ) ) {
        $compare = 'year';
    } elseif ( '%year%' === $permastructs[ $postname_index - 1 ] && ( isset( $query_vars['monthnum'] ) || isset( $query_vars['day'] ) ) ) {
        $compare = 'monthnum';
    } elseif ( '%monthnum%' === $permastructs[ $postname_index - 1 ] && isset( $query_vars['day'] ) ) {
        $compare = 'day';
    }

Here's the problem:

When get_option( 'permalink_structure' ) = '/%postname%/'
then $permastructs = array(0=>'%postname%');
and $postname_index = 0

Therefore, lines 379 and 381 are trying to access

$permastructs[ $postname_index - 1 ]

i.e.

$permastructs[-1]

which outputs a PHP Notice: Undefined offset: -1.

Needs to be adjusted as follows:

<?php
if ( 0 === $postname_index && ( isset( $query_vars['year'] ) || isset( $query_vars['monthnum'] ) ) ) {
        $compare = 'year';
    } elseif ($postname_index && '%year%' === $permastructs[ $postname_index - 1 ] && ( isset( $query_vars['monthnum'] ) || isset( $query_vars['day'] ) ) ) {
        $compare = 'monthnum';
    } elseif ($postname_index && '%monthnum%' === $permastructs[ $postname_index - 1 ] && isset( $query_vars['day'] ) ) {
        $compare = 'day';
    }

OR

<?php
if ( 0 === $postname_index) {
    if( isset( $query_vars['year'] ) || isset( $query_vars['monthnum'] ) ) ) {
        $compare = 'year';
    } 
} 
else {
    if ('%year%' === $permastructs[ $postname_index - 1 ] && ( isset( $query_vars['monthnum'] ) || isset( $query_vars['day'] ) ) ) {
        $compare = 'monthnum';
    } elseif ('%monthnum%' === $permastructs[ $postname_index - 1 ] && isset( $query_vars['day'] ) ) {
        $compare = 'day';
    }
}

[thomstark]

My second (last) bugfix has an error of its own, an extra closing parenthesis. Here's the fix to that:

<?php

if ( 0 === $postname_index) {
    if( isset( $query_vars['year'] ) || isset( $query_vars['monthnum'] ) ) {
        $compare = 'year';
    } 
} 
else {
    if ('%year%' === $permastructs[ $postname_index - 1 ] && ( isset( $query_vars['monthnum'] ) || isset( $query_vars['day'] ) ) ) {
        $compare = 'monthnum';
    } elseif ('%monthnum%' === $permastructs[ $postname_index - 1 ] && isset( $query_vars['day'] ) ) {
        $compare = 'day';
    }
}

[thakkarhardik]

Here is the patch for that resolves this warning. Please let me know if any changes are needed.

[thomstark]

Looks great. Thank you!

[garrett-eclipse]

Thanks for the patch @thakkarhardik and for confirming it's working @thomstark.

I feel you may have closed this in error @thomstark as the patch wasn't committed. The 'worksforme' closure status is to indicate the issues is a non-issue as it's working on a clean install. When you're moving a ticket forward that has a working patch it's better to leave it open and apply the 'has-patch' 'needs-testing' keywords.

I've updated the ticket accordingly.

[thomstark]

Thanks, yes. Closing was not intentional.

[thakkarhardik]

Thanks @garrett-eclipse. I am kind of a newbie here and unaware of how the testing is done in these kind of enhancements. Do we need to write unit tests for the above patch? Can you please guide briefly?

[SergeyBiryukov]

Reproduced the notice by visiting /?day=01 URL with the /%postname%/ structure. The patch looks good.

[SergeyBiryukov]

In 45214:

Permalinks: Avoid a PHP notice in wp_resolve_numeric_slug_conflicts() when visiting a day archive with the /%postname%/ permalink structure.

Props thakkarhardik, thomstark.
Fixes #46828.

[garrett-eclipse]

Hi @thakkarhardik sorry I just got your note, but doesn't look like I'm needed here. @SergeyBiryukov already tested and committed this fix so no unit tests or other actions needed.

[thakkarhardik]

Thanks @garrett-eclipse and @SergeyBiryukov .

[sabernhardt]

#41079 was marked as a duplicate.