这行PHP代码如何工作？

Question

How does it work?

// Purge obsolete login attempts
    $this->db->or_where('UNIX_TIMESTAMP(time) <', time() - $expire_period);

$this->db->or_where is codeigniter method,both 'UNIX_TIMESTAMP' and time() return timestamp, I can't figure out why 'UNIX_TIMESTAMP' will less than the 2nd argument.

Answer 1

time is a field in your database (most likely a datetime field) which is being converted to Unix timestamp format by your DB. So in theory it would be equivalent to writing this:

$this->db->or_where('time <', date('Y-m-d H:i:s', (time() - $expire_period)));