How to add an administrator with bcrypt password encryption in symfony?

I've encountered a "strange" issue while developing a website using symfony 2.6. I've already setup all the security stuff, including password encryption on registration (with bcrypt) to User and Admin entities. Now I want to add an admin and a user to try if my login engine works well, but obviously I cannot register a new user/admin with my website because of the security engine (i.e. i cannot access to the addUser page, because there's not an admin registered). I tried to create an admin directly from phpMyAdmin console but, at the moment when I put the admin's password, it is saved as plaintext (differently from the registration phase in my engine, that stores encrypted passwords), so the login fails.

So, how can i solve this issue?

Hope all of you understood this, otherwise feel free to ask!

Thanks in advance, Panc