String to Time

[treeleaf20]

I have the following code:

$now = strtotime("last sunday");
$sevendays = strtotime("+6 day", $now);
$startdate = strftime('%m/%d/%Y', $now);
$enddate = strftime('%m/%d/%Y', $sevendays);

I would like to be able to pass a date in a format like 12/14/2007 to this function and then find the original date to be 12/11/2007 which would be the original sunday of the week. This would be my start date that I use later. How would I go about doing this?

Thanks in advance!

[Weedpacket]

$then = strtotime('12/14/2007'); (though there are better formats to use)
.... the other lines you've written contain enough information about what to do with $then.