SugarCRM CE 6.5.x with php 5.6

I am trying to run SugarCRM 6.5 with php 5.6. I know it's not a good combination, but right now, I need to use this stack. (Maybe in a few months I can use SuiteCRM and php 7), but not now.

I have been able to install SugarCRM 6.5 and apparently it works fine, but I can not use the module constructor, because it does not save the changes (at least the new fields created)

Any ideas to solve this problem?

Thank you!