I don't know anything about symfony1 but I have just developed a massive web application in symfony2. So I like symfony2 very much. There are many projects in company which are in symfony 1.4.
Now I don't want to go back to learn symfony1.4. But I have to if I have no other option. I want to know that if I need to add extra features on existing wesite in symfony1.4.
Can I use symfony2 to make those extra features and leave old components in symfony1. Can I work together in symfony1 and symfony1.2