$key    Name of data point for which we're storing a value.
 *                       Accepts 'conditional', 'rtl' and 'suffix', 'alt', 'title' and 'path'.
 * @param mixed  $value  String containing the CSS data to be added.
 * @return bool True on success, false on failure.
 */
function wp_style_add_data( $handle, $key, $value ) {
	return wp_styles()->add_data( $handle, $key, $value );
}
<br />
<b>Fatal error</b>:  Uncaught Error: Failed opening required '/home/valigeria/public_html/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php' (include_path='.:/opt/alt/php81/usr/share/pear:/opt/alt/php81/usr/share/php:/usr/share/pear:/usr/share/php') in /home/valigeria/public_html/wp-settings.php:322
Stack trace:
#0 /home/valigeria/public_html/wp-config.php(111): require_once()
#1 /home/valigeria/public_html/wp-load.php(50): require_once('/home/valigeria...')
#2 /home/valigeria/public_html/wp-blog-header.php(13): require_once('/home/valigeria...')
#3 /home/valigeria/public_html/index.php(17): require('/home/valigeria...')
#4 {main}
  thrown in <b>/home/valigeria/public_html/wp-settings.php</b> on line <b>322</b><br />
<br />
<b>Fatal error</b>:  Uncaught Error: Call to a member function set() on null in /home/valigeria/public_html/wp-includes/l10n.php:854
Stack trace:
#0 /home/valigeria/public_html/wp-includes/l10n.php(957): load_textdomain('default', '/home/valigeria...', 'it_IT')
#1 /home/valigeria/public_html/wp-includes/class-wp-fatal-error-handler.php(49): load_default_textdomain()
#2 [internal function]: WP_Fatal_Error_Handler-&gt;handle()
#3 {main}
  thrown in <b>/home/valigeria/public_html/wp-includes/l10n.php</b> on line <b>854</b><br />