Zend certified PHP/Magento developer

Magento Cron Error unexpected ‘[‘

I’ve installed an extension to Magento that switches customers groups, the cron that it runs is giving me the following error:

TRIGGER: shutdown function Last error:

Array ( [type] => 4 [message] => syntax error, unexpected '[' [file] => /var/www/vhosts/xxxxxxxxx.com/httpdocs/app/code/local/Plugincompany/Groupswitch/Model/Mysql4/Rule/Collection.php [line] => 32 ) 
    if(!$ids) return $this;
    if(!is_array($ids)) $ids = array($ids);
    return $this->addFieldToFilter('rule_id', ['in' => $ids]);

Line 32 is the last line above. It’s running PHP 5.6.

Anyone got any ideas how to solve the issue?

Thanks.