Well I can tell you right now that it won't be able to directly interact with the device because that involves having access to the user's computer which is not possible with PHP unless it is running on the same machine.
So any one can get me some ideas for it without use of any specific sdk or dlls
You need to understand how complex such a task would be, and since you're asking if it can be done with PHP I can only assume that you do not know.
Ok, so I don't know specifically (how the readers, read) however, if I had to give you a quick overview then you would have to:
1) Process an image of the finger print;
2) Take details of the finger print
3) Match it with the sample data (trained).
If you understand how to do these concepts in C# then YES you could probably have this interact with PHP. For example, you could build the interface so it interacts (i.e. If the (processes) above return true, then the user can be signed in, else (processes) return false - do not let any further action).
Complex solution to this problem, without the use of libraries. I don't understand why you would want to re-invent the wheel, especially with little experience in this field (And it is a complex field). Have you tried looking at some academic papers in this field? This might be useful and provide you with an algorithm in which you can work from.
As mentioned this is probably beyond the scope of php. You may find php-gtk could do this, but I've had massive issues with getting it to work properly - but that may be me. The documentation is quite poor too.