how to get all combination of two dates with 20 minutes difference in php/codeigniter or either mysql

Question

I have this in my db:

I want to display doctor available time in in select box with difference of 20 minutes like from

2015-10-12 02:00:00 to 2015-10-12 04:00:00 what i need is

02:00:00
02:20:00
02:40:00
03:00:00
03:20:00
03:40:00
04:00:00

I tried this select '2015-10-12 02:00:00' + INTERVAL 20 MINUTE but it shows only one values i need all possible combinations.

Answer 1

User DateTime() , DateInterval() , and DatePeriod() to loop through that date period every 20 minutes and output the time. Note, we have to add a minute to the end time because DatePeriod does not include the last end time by default. Adding that minute will get the last time to be included.

$start    = new DateTime('2015-10-12 02:00:00');
$end      = (new DateTime('2015-10-12 04:00:00'))->modify('+1 minute');
$interval = new DateInterval('PT20M');
$period   = new DatePeriod($start, $interval, $end);
foreach($period as $date) {
    echo $date->format('H:i:s');
}

Demo