LIMIT和OFFSET - 如果offset大于行数或查询返回的记录少于5，则从头开始

I have a table vid and some records in it. By default first 5 records are displayed in the page. If a user clicks the button jquery runs ajax that runs php script and retrievs next 5 rows and returns the answer that replaces previous records on page and sp on. The problem is when the offset gets bigger than records left in table. Say I have 15 records. Firstly query takes first 5 records:I have a table vid and some records in it. By d