Fatal error: Uncaught Error: Call to undefined function wp_is_valid_utf8() in /var/www/wordpress/wp-includes/formatting.php:2287 Stack trace: #0 /var/www/wordpress/wp-includes/class-wp-taxonomy.php(378): sanitize_title_with_dashes('category_name') #1 /var/www/wordpress/wp-includes/class-wp-taxonomy.php(290): WP_Taxonomy->set_props('post', Array) #2 /var/www/wordpress/wp-includes/taxonomy.php(532): WP_Taxonomy->__construct('category', 'post', Array) #3 /var/www/wordpress/wp-includes/taxonomy.php(63): register_taxonomy('category', 'post', Array) #4 /var/www/wordpress/wp-settings.php(513): create_initial_taxonomies() #5 /var/www/wordpress/wp-config.php(151): require_once('/var/www/wordpr...') #6 /var/www/wordpress/wp-load.php(50): require_once('/var/www/wordpr...') #7 /var/www/wordpress/wp-blog-header.php(13): require_once('/var/www/wordpr...') #8 /var/www/wordpress/index.php(17): require('/var/www/wordpr...') #9 {main} thrown in /var/www/wordpress/wp-includes/formatting.php on line 2287