🐞 Issues reported in debug.log

[KTS915]

Expected behavior

Empty log

Current behavior

[19-Jun-2023 14:15:36 UTC] PHP Deprecated:  ltrim(): Passing null to parameter #1 ($string) of type string is deprecated in /wp-includes/formatting.php on line 4414

[19-Jun-2023 14:15:36 UTC] PHP Deprecated:  ltrim(): Passing null to parameter #1 ($string) of type string is deprecated in /wp-includes/formatting.php on line 4414

[19-Jun-2023 14:15:43 UTC] PHP Fatal error:  Uncaught TypeError: Cannot access offset of type string on string in /wp-admin/includes/class-wp-site-health.php:3053

Stack trace:
#0 /wp-includes/class-wp-hook.php(308): WP_Site_Health->wp_cron_scheduled_check()
#1 /wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters()
#2 /wp-includes/plugin.php(565): WP_Hook->do_action()
#3 /wp-cron.php(188): do_action_ref_array()
#4 {main}
  thrown in /wp-admin/includes/class-wp-site-health.php on line 3053

[19-Jun-2023 14:15:43 UTC] PHP Fatal error:  Uncaught TypeError: call_user_func(): Argument #1 ($callback) must be a valid callback, no array or string given in /wp-includes/functions.php:3722

Stack trace:
#0 /wp-includes/class-wp-fatal-error-handler.php(239): wp_die()
#1 /wp-includes/class-wp-fatal-error-handler.php(154): WP_Fatal_Error_Handler->display_default_error_template()
#2 /wp-includes/class-wp-fatal-error-handler.php(58): WP_Fatal_Error_Handler->display_error_template()
#3 [internal function]: WP_Fatal_Error_Handler->handle()
#4 {main}
  thrown in /wp-includes/functions.php on line 3722

Possible solution

No response

Steps to reproduce bug

Load a page

Context

No response

ClassicPress version

2.0

PHP version

8.1

Can you help?

I can help test a solution

[mattyrob]

@KTS915 - what theme and plugins are you using? I'm not seeing any of the ltrim() issues logged on my sites.

There is a fix for the Site Health section in #121

[KTS915]

I'm running no plugins and the default 2015 theme. But I have now identified that the ltrim() issues seem to be caused when a new page (on front-end or back-end) is visited immediately after my APCu object cache is cleared, so it's extremely hard to pin down what the real cause is.

I can see that ltrim() on line 4414 of /wp-includes/formatting.php is being run within the esc_url() function, so obviously what's happening somewhere is that there's an attempt to escape a URL that doesn't exist. But who knows where that non-existent URL is coming from ?!

[xxsimoxx]

Seem two different issues.

• One is fixed in Fix version check in Site Health #121
• The other is a PHP compatibility issue that seems to be in many places, mainly in wp-includes/formatting.php. For this one maybe we can wait a fix for WP, even if fixing this is easy, so we handle those cases the same way.

[mattyrob]

A potential fix for the ltrim() issue is to replace the early check in the function from:

if ( '' === $url ) {

To:
if ( empty( $url ) ) {

[KTS915]

So that solution suggests that what's happening is that somewhere core is trying to escape something that's an object (or array, or integer, etc) and not a string. In that case, @mattyrob's "potential fix" is the right way to go.

[xxsimoxx]

Here we used the null coalesce operator.

[KTS915]

But do we know it's an object here and not an array? If it's an array, null isn't correct.

[mattyrob]

According to upstream documentation esc_url() should be passed a string. The fucntion checks for and returns early is passed an empty string. I honestly don't know what happens if you pass an array or object (but it is an incorrect use of the function).

The errors we are seeing is because passing null to the function - so perhaps passing a variable that is undefined will pass the first conditional check because null is not the same as an empty string. But, when null is passed to ltrim PHP now flags a deprecation notice.

Using empty() is a good way to check for null and an empty string. But perhaps you are correct and the function should handle incorrect usage much better - maybe a check for is_string() and bail out with _doing_it_wrong() if that check fails.

[xxsimoxx]

I think we should return the same values as before, as an example:

$x = wp_kses( null, array() );
var_dump( $x );
string(0) ""

So return an empty string on null.

[Soenke2]

... I have already reported about the same error (deprecation) with formatting.php, line 4414, and it still exists (php 8.1 and 8.2) ...