Getting some warnings/errors related to Hummingbird cache on the frontend of my site

I’m getting these errors on the frontend of my site:
Warning: preg_match(): Compilation failed: nothing to repeat at offset 35 in /home//+++.com/wp-content/plugins/wp-hummingbird/core/modules/class-module-page-cache. php on line 470

Warning: Cannot modify header information - headers already sent by (output started at /home//m.s.com/wp-content/plugins/wp-hummingbird/core/modules/class-module-page-cache. php:470) in /home//+++/wp-content/plugins/wp-hummingbird/core/modules/class-module-page-cache. php on line 975

Warning: Cannot modify header information - headers already sent by (output started at /home//+++/wp-content/plugins/wp-hummingbird/core/modules/class-module-page-cache. php:470) in /home//m.s.com/wp-content/plugins/wp-hummingbird/core/modules/class-module-page-cache. php on line 975

Warning: Cannot modify header information - headers already sent by (output started at /home//+++/wp-content/plugins/wp-hummingbird/core/modules/class-module-page-cache. php:470) in /home//m.s.com/wp-content/plugins/wp-hummingbird/core/modules/class-module-page-cache. php on line 975

Warning: Cannot modify header information - headers already sent by (output started at /home//+++/wp-content/plugins/wp-hummingbird/core/modules/class-module-page-cache. php:470) in /home//+++/wp-content/plugins/wp-hummingbird/core/modules/class-module-page-cache. php on line 979

  • Adam Czajczyk

    Hello Jean Pierre,

    I hope you're well today and thank you for your question!

    I checked the site and the issue was caused by "Exclusions" list on "Hummingibird -> Caching -> Page Cache" settings page. In addition to default rule, there were these three lines added:

    *\/checkout\/*
    *\/cart\/*
    *\/account\/*

    I assume that the goal here was to exclude entirely all the pages that include "checkout", "cart" and "account" slugs. However, if you test these lines with a regex validator (e.g here https://www.freeformatter.com/regex-tester.html) you will find that they report exactly the same error "Nothing to repeat" - they are not valid here.

    In order to exclude those pages it would suffice to use these strings:

    /checkout/
    /cart/
    /account/

    I set the exclusion list like that and the error is now gone.

    I hope that helps and if you have any additional questions, let me know please.

    Kind regards,
    Adam