PHP 8.1: fix passing null to non-nullable deprecation

[mustafauysal]

It seems rtrim() expects to be passed a non-nullable string on PHP 8.1. Passing null results rtrim(): Passing null to parameter #1 ($string) of type string is deprecated notice.

Ref:

• https://wiki.php.net/rfc/deprecate_null_to_scalar_internal_arg

[lomeraniel]

Noting here that a VIP customer is facing this issue:

"rtrim(): Passing null to parameter #1 ($string) of type string is deprecated"

Trace from QM:
wp-includes/formatting.php:2827
rtrim()
wp-includes/formatting.php:2827
untrailingslashit()
wp-includes/formatting.php:2812
trailingslashit()
wp-content/mu-plugins/http-concat/concat-utils.php:27
WPCOM_Concat_Utils::realpath()
wp-content/mu-plugins/http-concat/cssconcat.php:84
WPcom_CSS_Concat->do_items()
wp-includes/functions.wp-styles.php:68
wp_print_styles()
wp-includes/class-wp-hook.php:310
do_action('wp_head')
wp-includes/general-template.php:3053
wp_head()
wp-content/themes/dispatch/header.php:48
load_template('wp-content/themes/dispatch/header.php')
wp-includes/template.php:720
locate_template()
wp-includes/general-template.php:48
get_header()
wp-content/themes/dispatch/front-page.php:15

[mustafauysal]

@lomeraniel could you give it a try on the root domain without having a trailingslash? ( e.g. example.com without / at the end )

[bytesizeguru]

Another VIP customer reporting the same issue today:

Deprecated rtrim(): Passing null to parameter [#1](https://wordpressvip.zendesk.com/agent/tickets/1) ($string) of type string is deprecated 183
wp-includes/formatting.php:2827
MU Plugin: http-concat
wp-includes/formatting.php:2827
rtrim()
wp-includes/formatting.php:2827
untrailingslashit()
wp-includes/formatting.php:2812
trailingslashit()
wp-content/mu-plugins/http-concat/concat-utils.php:27
WPCOM_Concat_Utils::realpath()
wp-content/mu-plugins/http-concat/cssconcat.php:84
WPcom_CSS_Concat->do_items()
wp-includes/script-loader.php:2244
print_admin_styles()
wp-includes/class-wp-hook.php:310
do_action('admin_print_styles')
wp-admin/admin-header.php:132

[rodruiz]

VIP customer here. We are having the same issue on our dev environment.

wp-includes/formatting.php:2827
rtrim()
wp-includes/formatting.php:2827
untrailingslashit()
wp-includes/formatting.php:2812
trailingslashit()
wp-content/mu-plugins/http-concat/concat-utils.php:27
WPCOM_Concat_Utils::realpath()
wp-content/mu-plugins/http-concat/cssconcat.php:84
WPcom_CSS_Concat->do_items()
wp-includes/functions.wp-styles.php:68
wp_print_styles()
wp-includes/class-wp-hook.php:310
do_action('wp_head')
wp-includes/general-template.php:3053
wp_head()
wp-content/themes/rjth2019/header.php:44
load_template('wp-content/themes/rjth2019/header.php')
wp-includes/template.php:720
locate_template()
wp-includes/general-template.php:48
get_header()
wp-content/themes/rjth2019/single-post.php:21

[emreerkan]

LGTM

[rebeccahum]

Reproduced, fix works thanks