I have a huge table that PHP gets from a db and displays. Every time php echos a few rows of the table, it flushes the output. So from the client's point of view, the table is basically growing bigger every few seconds.
Look at using something like Slickgrid which can display Millions of records quickly and efficiently. You should not be trying to do this with PHP buffers.
I personally use it with a dataset of 100,000 rows and it is lightning fast.