Looking for best possible solution assigning TASK to Users

I'm creating a simple program in php that manages task to different users. And each task will be given to users in sequence or one by one entry to Table Task. Assuming I have (Task Table) and (Users Table), once a new record in task table enters it will be assigned to an online user. For example we have 3 online users. If a new task enters to table TASK it will be assigned to USER1 then if another task again enters to task table now it will be assigned to USER2 . So we now have TASK1 assigned to USER1 and TASK2 assigned to USER2. if another enters the task table it will be assigned to USER3. Then if a fourth or more TASK enters the table again it will be assigned to USER1 again and the flow continues. Can anyone help me create an optimize algorithm for this. Thanks!