Hi,
Thank you for the details, I may have found something there. I googled a bit, and found that on very rare cases, there is a certain PHP directive activated, which may report a fatal error, when declaring arrays as ‘[]’ instead of ‘array()’. There is very little information about this, but I am pretty sure, that this is the issue here.
To resolve it, you will have to replace one of the plugin file contents. Please let me know if you need help with that. Instructions:
1. Open up the wp-content/plugins/ajax-search-pro/includes/classes/etc/class-asp_helpers.php file on your server
2. Replace it’s contents with this
3. Save, and now try to activate the plugin
I’m 99% positive this is going to resolve the problem. In that case, I will make sure to include this as a permanent fix in the upcoming release.