Undefined function mb_strpos

As soon as I enable this extension on my site, I get the following error about mb_strpos being undefined: Fatal error: Uncaught Error: Call to undefined function Woo_Store_Vacation\Settings\Sections\mb_strpos() in /public_html/wp-content/plugins/woo-store-vacation/src/Settings/Sections/Section.php:42 Stack trace: #0 [internal function]: Woo_Store_Vacation\Settings\Sections\Section::Woo_Store_Vacation\Settings\Sections{closure}(‘section_title’) 1 /public_html/wp-content/plugins/woo-store-vacation/src/Settings/Sections/Section.php(43): array_filter(Array, Object(Closure)) 2 /public_html/wp-content/plugins/woo-store-vacation/src/Settings/Sections/Conditions.php(101): Woo_Store_Vacation\Settings\Sections\Section->get_field_keys() 3 /public_html/wp-content/plugins/woo-store-vacation/src/WooCommerce/Vacation.php(95): Woo_Store_Vacation\Settings\Sections\Conditions->get_active() 4 /public_html/wp-includes/class-wp-hook.php(310): Woo_Sto in /public_html/wp-content/plugins/woo-store-vacation/src/Settings/Sections/Section.php on line 42 According to the answers on this StackOverflow question , mbstring is a nonstandard/nondefault library in PHP, and PHP needs to be custom-built to support it. We’ve never had a problem with missing PHP functionality with any other extensions or any of our own site code. Shouldn’t this WooCommerce Store Vacation extension work with basic PHP methods and not require custom/special PHP functionality? This topic was modified 2 years, 7 months ago by WP User .