How do I connect two tables

That doesn't make a lot of sense as stated: you have four ID values:
studentlogin.id, studentlogin.login_id, studentreg.id, and studentreg.loginid
And as a result, there is no direct link between them.
Plus, we have no idea which of the two "loginid" values you want to display, or how they are supposed to be kept together.
Have a think about it for a few minutes, and try describing the actual set of processes that need to happen when a student registers, and what values need to be stored and / or fetched from where.
Then try to explain that to us!
Use the "Improve question" widget to edit your question and provide better information.

I assume you have two tables as follows:

studentlogin with fields : id,name,age,address,login_id
studentreg with fields : id,login_id.

Now there can be a relationship between them only if you have "one" common field in both. Can you answer these questions, in order for me to get a clear idea?

1. Why have you used login_id in both tables?
2. In which table will you actually store the value of login_id? in login table or reg table?
3. How will the login_id value be generated?
4. In which table are you referencing the field login_id as a foreign key?
5. From which table do you want to display the data if the user clicks the button?

Please answer these questions and I might be able to help you out!

- Cheers

Use id as the primary key, or u can add one more value to the table, i.e name and connect that. its better not to use both id and login_id together. Keep one.

what are all the things u received when registration..