I’m Graduated in Masters of infromation technology mangement after graduating i use my OPT and it expried.I’m thinking to do PHD after graduating in PHD i’m eligible for OPT again? How soon i can get green card with PHD degree ?Which catgory the green card comes falls under for PHD?

Yes you can get OPT again after completion of your PhD. What category you qualify for a GC depends on your job, if it’s employment based. After completion of your PhD you can approach us for an evaluation of EB-1 or EB-2 categories. If you are working as a researcher and have enough publications you might qualify for EB-1.