This is a bit of an annoying one since the project does not seem to be maintained actively anymore and Xenforo ships with the latest release (0.8.11), but this issue (the
$key in the array_walk callable function must not be by reference) has been PR'd and merged in their master branch.This never worked anyway and was silently ignored by older PHP versions, but since 8.0 it starts throwing a fit when used
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