Since upgraded to Rules 7.x-2.1+2-dev (2012-Apr-02), I constantly got PHP warnings like following
Warning: array_diff_key() [function.array-diff-key]: Argument #1 is not an array in RulesEventSet::rebuildEventCache() (line 750 of sites/all/modules/rules/includes/rules.plugins.inc).
Warning: array_keys() [function.array-keys]: The first argument should be an array in RulesEventSet::rebuildEventCache() (line 750 of sites/all/modules/rules/includes/rules.plugins.inc).
Warning: array_flip() [function.array-flip]: The argument should be an array in RulesEventSet::rebuildEventCache() (line 751 of sites/all/modules/rules/includes/rules.plugins.inc).
This module is used by module Entity tokens and Entity API on my sites.
The first argument is $events, which is initialized by calling "$events = rules_fetch_data('event_info');". What I'm thinking is, in case variable $events is initialized with a NULL value (or a non-array value that indicates there no data for it), and there is no rules set up, function call "array_diff_key($events, $sets)" on line 750 won't work. I don't know much about this module, so this is just my guess.
Anyway, since the bug annoy me a lot, I'm going to downgrade to 7.x-2.1.
Thanks
Closed: outdated
2.0
Rules Core
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
Drupal 7 is no longer supported.
The root cause of this problem with class loading in systems (both PHP and Drupal) that were not really designed for object-oriented programming. But the class loader in PHP and Drupal has been considerably overhauled in newer versions of PHP and Drupal, and we no longer experience any problems like this.