PHP: Dynamic Calendar (easiest ever)

<style type="text/css">
<!--
  td
  {
    font-size:12pt;
    line-height:14pt;
    font-family:Helvetica,Arial;
  }
//-->
</style>

<?PHP

## change to the previous month
if ($command == "prev_month")
{
  if (--$month == 0)
  {
    $month = 12;
    $year--;
  }
}
## change to the next month
else if ($command == "next_month")
{
  if (++$month == 13)
  {
    $month = 1;
    $year++;
  }
}

## if no month has been passed
if ($month == "")
{
  $year= date("Y");
  $month= date("n");
  $month_name = date("F",mktime(0,0,0,$month,1,$year));
}
## use current date if no month is passed
else
{
  $year= date("Y",mktime(0,0,0,$month,1,$year));
  $month= date("n",mktime(0,0,0,$month,1,$year));
  $month_name = date("F",mktime(0,0,0,$month,1,$year));
}


$dow = date("w",mktime(0,0,0,$month,1,$year));  //which day 1 falls on in the week
(0 = Sun)
$dim = date("d",mktime (0,0,0,$month+1,0,$year)); //days in the current month
## modification to only print the number of weeks in a month
$wim = ceil(($dim+$dow)/7); //weeks in month

$ct=0;

echo "<br>
<table border='0' cellpadding='1' cellspacing='1' width='425' align='center'>
<tr>
  <td align='center'><h1><a href='index.php?
command=prev_month&month=$month&year=$year'><<</a> $month_name $year <a
href='index.php?command=next_month&month=$month&year=$year'>>></a></h1></td>
</tr>
</table>
<table border='1' cellpadding='1' cellspacing='1' width='425' align='center'>
<tr>
  <td  align='center'><b>Sun</td>
  <td  align='center'><b>Mon</td>
  <td  align='center'><b>Tue</td>
  <td  align='center'><b>Wed</td>
  <td  align='center'><b>Thu</td>
  <td  align='center'><b>Fri</td>
  <td  align='center'><b>Sat</td>
</tr>
  ";

## print only the number of weeks needed
for($row=1;$row<$wim+1;$row++)
{  
  echo "<tr height='60'>";  

  ## prints week (Sun to Sat)
  for($week=1;$week<8;$week++)  
  {  
    $ct++;  
    $value=mktime(0,0,0,$month,$ct-$dow,$year);  
    
    ## if $value is part of current month
    if (date("m",$value)==$month)  
    {  
      echo "
      <td align='center' class='body' width='85' valign='top'>
        <div align='right'><b>".date("j",$value)."</a></b></div><br>
      </td>";  
    }  
    ## print previous and next month dates, but grayed out
    else
    {
      echo "<td align='center' class='body' width='85' valign='top'
bgcolor='#CCCCCC'><div
align='right'><b>".date("j",$value)."</a></b></div><br></td>";
    }  
  }
  
  echo "</tr>";
}  


echo "</table>";  

?>