GetRecords.php

<?php

// Select all the dates in from 01 August 2018 to 31 August 2018
$dates = $this->db->query("select substring(checktime, 1, 10) as date from checkinout where substring(checktime, 1, 10) < '2018-08-31' and substring(checktime, 1, 10) > '2018-08-01' group by date;
");

foreach ($dates->result() as $date)
{
  // Now select the records for the particular date.
  $attendance = $this->db->query("select  userid, username, times.timez as time from (select logid,userid,username, substring(checktime, 11) as timez, substring(checktime, 1, 10) as time from checkinout where substring(checktime, 1, 10) = '$date' order by timez asc) as times where times.logid = logid group by userid;");
  
  foreach($attendance->result() as $dateAttendance)
  {
    // Do something with the records for $date.
  }
}