Description:
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When date_modify() is given the last day of a month and asked to add one weekday (e.g. +1 Sunday), if the last day of the month is that same weekday, then date_modify() doesn't add a week-- it returns the same date it was given.

This problem occurs in PHP 5.2.9.  It doesn't occur in PHP 5.2.6, which returns the correct result.


Reproduce code:
---------------
<?php
echo "PHP Version = ", phpversion(), "\n";
$dt = new DateTime();
date_date_set($dt, 2009, 5, 31);
echo 'Before date_modify: ', $dt->format('l m/j/y'), "\n";
$action = "+1 Sunday";
date_modify($dt, $action);
echo "After date_modify ($action): ",  $dt->format('l m/j/y') , "\n",
    "Should be Sunday 6/7/09\n";
?>


Expected result:
----------------
PHP Version = 5.2.6-3ubuntu4.1
Before date_modify: Sunday 05/31/09
After date_modify (+1 Sunday): Sunday 06/7/09
Should be Sunday 6/7/09


Actual result:
--------------
PHP Version = 5.2.9-2
Before date_modify: Sunday 05/31/09
After date_modify (+1 Sunday): Sunday 05/31/09
Should be Sunday 6/7/09