PHP Warning: Array to string conversion error appears with PHP 8.1 (maybe previous versions too)

[DjiXas]

Just noticed this, cannot reproduce or figure out why it appears, but there are few random instances in the error log

[12-May-2024 08:13:17 UTC] PHP Warning: Array to string conversion in /homepublic_html/wp-includes/formatting.php on line 1108

[swissspidy]

Hi there and welcome to WordPress Trac!

Such warnings usually occur when a plugin is using a WP-provided function in an incorrect way. In this case it's the wp_check_invalid_utf8() function. I recommend checking your active plugins & theme whether they are using that function somehow (usually through esc_html() or esc_js(). Just because the error message mentions wp-includes doesn't mean the error is also originating from WordPress. It's just where the error eventually happened.