Calendar generation strange fail

Question

I set out to generate a array containing a 12-month calendar starting on this (now) month. This is for a particular application, and requires special code, so I cannot use calendar libraries.

Here's the code I have:

header('Content-type: text/plain');

$Cal1 = array();

$now = new fTimestamp('now');
$now = $now->modify('Y-m-1 00:00:00');

for ( $i = 0; $i < 12; $i++ ) {
 if ( $i > 1 ) {
  $then = $now->adjust("+$i months");
 }
 elseif ( $i == 1 ) {
  $then = $now->adjust("+1 month");
 }
 else {
  $then = $now;
 }
 $thisMonth = $then->format('F');
 $Cal1[$thisMonth] = array();
 $thisMonthDays = $then->format('t');
 for ( $j = 0; $j < $thisMonthDays; $j++ ) {
  if ( $i > 1 ) {
   $then = $then->adjust("+$i days");
  }
  elseif ( $i == 1 ) {
   $then = $then->adjust("+1 day");
  }
  $thisDate = $then->format('j');
  $thisDay = $then->format('l');
  $Cal1[$thisMonth][$thisDate] = $thisDay;
 }
}

var_dump($Cal1);

This should generate an array of the form:

array {
    ["Month_Name"] => array {
        [Day_Number] => "Day_Name"
        etc...
    }
    etc...
}

The script outputs the right number of months, but not the right number of days... The full dump is quite lengthy, so I'll only post October, February, and March:

array(12) {
  ["October"]=>
  array(1) {
    [1]=>
    string(6) "Friday"
  }
  ["February"]=>
  array(22) {
    [5]=>
    string(8) "Saturday"
    [9]=>
    string(9) "Wednesday"
    [13]=>
    string(6) "Sunday"
    [17]=>
    string(8) "Thursday"
    [21]=>
    string(6) "Monday"
    [25]=>
    string(6) "Friday"
    [1]=>
    string(7) "Tuesday"
    [29]=>
    string(7) "Tuesday"
    [2]=>
    string(8) "Saturday"
    [6]=>
    string(9) "Wednesday"
    [10]=>
    string(6) "Sunday"
    [14]=>
    string(8) "Thursday"
    [18]=>
    string(6) "Monday"
    [22]=>
    string(6) "Friday"
    [26]=>
    string(7) "Tuesday"
    [30]=>
    string(8) "Saturday"
    [4]=>
    string(9) "Wednesday"
    [8]=>
    string(6) "Sunday"
    [12]=>
    string(8) "Thursday"
    [16]=>
    string(6) "Monday"
    [20]=>
    string(6) "Friday"
    [24]=>
    string(7) "Tuesday"
  }
  ["March"]=>
  array(19) {
    [6]=>
    string(6) "Sunday"
    [11]=>
    string(6) "Friday"
    [16]=>
    string(9) "Wednesday"
    [21]=>
    string(6) "Monday"
    [26]=>
    string(8) "Saturday"
    [31]=>
    string(8) "Thursday"
    [5]=>
    string(8) "Thursday"
    [10]=>
    string(7) "Tuesday"
    [15]=>
    string(6) "Sunday"
    [20]=>
    string(6) "Friday"
    [25]=>
    string(9) "Wednesday"
    [30]=>
    string(6) "Monday"
    [4]=>
    string(6) "Monday"
    [9]=>
    string(8) "Saturday"
    [14]=>
    string(8) "Thursday"
    [19]=>
    string(7) "Tuesday"
    [24]=>
    string(6) "Sunday"
    [29]=>
    string(6) "Friday"
    [3]=>
    string(9) "Wednesday"
  }

Now, what's the matter?

Answer 1

Doesn't directly answer your question, but I'd do it a lot simpler like so:

$cursor = mktime(0, 0, 0, date('m'), 1);
$end = strtotime('+1 year', $cursor);

$out = array();

while ($cursor < $end) {
    $out[date('F', $cursor)][date('j', $cursor)] = date('l', $cursor);
    $cursor = strtotime('+1 day', $cursor);
}

var_dump($out);

To directly answer your question, you're always adjusting $then relative to itself with increasingly bigger numbers, hence you're skipping days and are getting funky numbers.

 for ( $j = 1; $j < $thisMonthDays; $j++ ) {
     $then = $then->adjust("+$i days");
 }

1. $then is the 1st, you add 1 (first iteration)
2. $then is the 2nd, you add 2 (second iteration)
3. $then is the 4th, you add 3
4. $then is the 7th, you add 4
5. etc pp.