Why does iterating over weeks go wrong with PHP date?
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I'm writing a php script that iterates over the Monday of each week. 

However the script seemed to get out of sync after 22nd of October.

    <?php
    
    $october_8th = strtotime("2012-10-08");
    
    $one_week = 7 * 24 * 60 * 60;
    
    $october_15th = $october_8th + $one_week;
    $october_22nd = $october_15th + $one_week;
    $october_29th = $october_22nd + $one_week;
    $november_5th = $october_29th + $one_week;
    
    echo date("Y-m-d -> l", $october_8th) . '<br />';
    echo date("Y-m-d -> l", $october_15th) . '<br />';
    echo date("Y-m-d -> l", $october_22nd) . '<br />';
    echo date("Y-m-d -> l", $october_29th) . '<br />';
    echo date("Y-m-d -> l", $november_5th) . '<br />';

This would output:

    2012-10-08 -> Monday
    2012-10-15 -> Monday
    2012-10-22 -> Monday
    2012-10-28 -> Sunday
    2012-11-04 -> Sunday

I would expect it to say the 29th of October but it gets stuck at the 28th.

How should I get around this problem?