Add function page for wp_is_valid_utf8 #2192
Description
What is the new page you are requesting?
In the latest stable release, since WordPress 6.9.0, there are new deprecation warnings shown to developers:
PHP Deprecated: Function seems_utf8 is deprecated since version 6.9.0! Use wp_is_valid_utf8() instead.
The same migration was also published on the make blog three months ago:
https://make.wordpress.org/core/2025/11/18/modernizing-utf-8-support-in-wordpress-6-9/
The blog post was probably written before the stable release, so I can understand the documentation was not ready at that time. But it seems like an oversight to release 6.9.0 with deprecation warnings nudging developers to adopt a function that is not yet documented.
- "Sorry, but nothing matched your search terms." — https://developer.wordpress.org/?s=wp_is_valid_utf8
- https://developer.wordpress.org/reference/functions/seems_utf8/
How will this new page help you?
Aid in migration through usage examples, understanding differences, and potentially engage in the comment thread to hear about issues I might run into and sharing solutions.
See also:
- [DevHub] Add function page for wp_scrub_utf8 #2159
- Fix docs build: php-parser 4.x, vendored dependency phpdoc-parser#251
Workaround
I'm reading the source code for now. There are high-quality doc blocks, which I believe the website will eventually use to generate its web pages:
seems_utf8: https://github.com/WordPress/WordPress/blob/6.9.1/wp-includes/formatting.php#L884wp_is_valid_utf8: https://github.com/WordPress/WordPress/blob/6.9.1/wp-includes/utf8.php#L4 and https://github.com/WordPress/WordPress/blob/6.9.1/wp-includes/compat-utf8.php#L258
There is also the original commit (WordPress/WordPress@ede3a79).