Fatal Error

The findings are correct, because the search includes every mention of Aelia_WC_RequirementsChecks, including declaration, usage and documentation. Based on what we can see, if you search for class Aelia_WC_RequirementsChecks, then you should get four results.

Based on the returned output, I would speculate that the issue could be stemming from the Blacklister, or the Aelia Foundation Classes plugin which might be too old and include an obsolete version of the Aelia_WC_RequirementsChecks class. For reference, the latest version of the Blacklister is 1.1.2.210622, while the Aelia Foundation Classes is 2.1.12.210628.

If the versions installed on your site are older, you can verify my hypothesis by disabling the Blacklister and/or the Aelia Foundation Classes plugin, and see if that solves the issue.

Aha that was it. I had a totally different version of the blacklister plugin, it was a free version I think, I notice on your site that there is only a commercial version. I’ve removed the blacklister plugin and the issue has gone. Thanks!

Thanks for the confirmation. I’m glad to hear that the issue has been solved.

Indeed, the Blacklister used to be a free plugin. We had to replace it with a premium version, much like the EU VAT Assistant, to be able to keep maintaining it. We kept both versions up to date for about a year, but it’s possible that the crucial change to the requirement checking class was introduced at a later stage.

Note
If you copy file aelia-wc-requirementscheck.php from the Aelia Foundation Classes to the Blacklister folder, overwriting the existing (old) one, you could also be able to keep using that plugin as well. We haven’t tested this kind of fix in such an old plugin, but it should be easy enough to verify this hypothesis.