Getting first day of every week in 6 months - php

Question

I'm trying to figure out how can I get the the first day of week for the last 6 months and can't get to a working solution.
If I write date("Y-m-d 00:00:00", strtotime("-1 week", date("Y-m-d")); It just subtracts 7 days from the current date; what I want to do is to always return the date of Monday from that week.
Expected result:
2011-8-8 00:00:00
2011-8-1 00:00:00
2011-7-25 00:00:00
2011-7-18 00:00:00
etc

Answer 1

This should do it:
for ($i=0; $i<52/2; $i++)
echo date('Y-m-d', mktime(1, 0, 0, date('m'), date('d')-date('w')-$i*7+1, date('Y'))) . " 00:00:00\n";
it's slightly changed from Mike's Post, who wants the sunday instead of the monday.

Answer 2

I'd recommend DateTime::createFromFormat.
Pre-PHP 5.3, you can use strtotime instead:
<?php
define('NUM_WEEKS', 10);
$dates = Array();
$dates[] = strtotime('Monday');
for ($i = 0; $i < NUM_WEEKS-1; $i++)
$dates[] = strtotime('-1 week', $dates[$i]);
foreach ($dates as $date)
echo strftime('%c', $date) . "\n";
?>
Output:
Mon Aug 22 00:00:00 2011
Mon Aug 15 00:00:00 2011
Mon Aug 8 00:00:00 2011
Mon Aug 1 00:00:00 2011
Mon Jul 25 00:00:00 2011
Mon Jul 18 00:00:00 2011
Mon Jul 11 00:00:00 2011
Mon Jul 4 00:00:00 2011
Mon Jun 27 00:00:00 2011
Mon Jun 20 00:00:00 2011
Live demo.

Answer 3

If you're trying to make Saturday (or any other day for that matter)
the first day of the week to select datasets, here's a good
workaround:
<?php $last_sat=date("z", strtotime("last Saturday"));
$second_last_sat=date("z", strtotime("last Saturday-1 week")); ?>
source: http://www.php.net/manual/en/function.strtotime.php
What you'd probably want is
<?php $last_mon=date("z", strtotime("last Monday "));
$second_last_mon=date("z", strtotime("last Monday-1 week")); ?>
etc..