Insert weekly info from date and time php - php

Question

I have a function that is accepting the date and time, and number of occurrences of an episode. I'm using a while loop to try and insert and episode every week on the same day and time. For example if the episode is monday at 7PM, i want to insert in for every monday at 7PM for the number of occurrences given.
Here's my code and while loop:
$sEpsAirDate = strtotime($aVars['air_date'].' '.$aVars['air_time'].$aVars['air_ampm']);
$i = 1;
while ($i <= $aVars['repeat_count']) {
$sEpsAirDate = // How can I alter this variable to change the date to every week?
db_res(
"INSERT INTO `hm_episodes_main` SET
`show_id` = '{$aVars['show_id']}',
`title` = '{$sEpsTitle}.{$i}',
`season` = '{$aVars['eps_season']}',
`uri` = '{$sUri}.{$i}',
`desc` = '{$sEpsDesc}',
`air_date` = '{$sEpsAirDate}'
");
$i++
}
How would I alter the $sEpsAirDate variable to be entered accurately on every day of the week on the given time?

Answer 1

Use mktime():
$next_ep_timestamp = mktime ($hour,$min,$sec, $first_ep_month, $first_ep_day + 7 * $weekcount, $first_ep_year);
"Init" this by setting the respective variables for the date, month and year of the first episode, then you can create new dates for following weeks by adding increments of 7 to the day-parameter in mktime (like shown above).
Then format for output to SQL like this:
$datetime_str = date("Y-m-d H:i:s", $next_ep_timestamp);
//gives a date-str like '2011-10-16 12:59:01'

Answer 2

The first idea that comes to my mind is just adding the seconds in a week to the sEpsAirDate with every iteration in the loop:
$sEpsAirDate += 604800;
If you needed to preserve the first air date you could copy it out into a separate variable and then do something like this (change the LCV $i to start at 0):
$sEpsAirDate = $sEpsFirstAirDate+(604800*$i);
But this method has the potential to create problems with Daylight Savings Time... so it might be safer to break the date into year, month and day variables and then recreate the $sEpsAirDate with every loop iteration by adding ($i*7) to day. ... So something like (again change the LCV $i to start at 0):
$sEpsAirDate = mktime($sEpsAirDateHour, $sEpsAirDateMinute, 0, $sEpsAirDateMonth, $sEpsAirDateDay+($i*7), $sEpsAirDateYear);