PHP 초보입니다.

아래는 2005년 9월 달력 소스 인데,
30일(마지막 일) 이후
날짜가 계속 진행됩니다.
1일, 2일 3일 이런식으로 계속 나오는데
어디가 틀렸는지 잘 모르겠네요


::: 아래 소스 :::

<?

$month=date("m");
$today=date("Y-m-d");

function car($year,$month) {

        echo "$year년 $month월 달력입니다.<p>";
        $lastday=date("t",mktime(0,0,0,date("d"),$year));
        $tday2=date("D",mktime(0,0,0,$month,1,$year));

                switch($tday2)         {
                        case "Sun";
                        $a=1;
                        break;

                        case "Mon";
                        $a=2;
                        break;
                        
                        case "Tue";
                        $a=3;
                        break;

                        case "Wed";
                        $a=4;
                        break;

                        case "Thu";
                        $a=5;
                        break;

                        case "Fri";
                        $a=6;
                        break;

                        case "Sat";
                        $a=7;
                        break;
                }

                echo("

                <table border=1>
                        <tr>
                                <td>일</td>
                                <td>월</td>
                                <td>화</td>
                                <td>수</td>
                <td>목</td>
                                <td>금</td>
                                <td>토</td>
                        </tr>

                        ");

                        $b=1;

                        for($k=1;$k<=6;$k++) {
                                echo"<tr>";
                                        for($i=1;$i<=7;$i++) {
                                        echo"<td>";
                                        if($a == $i || $b >1) {
                                                echo $b;

                                                if($b>=$lastday) {
                                                        $b=""; }
                                                        $b++;
                                        }
                                        echo"</td>";
                                        }
                                        echo "</tr>";
                        }
                        echo"</table>";
}

car(2005,9);



?>


고수님들의 많은 도움 기다리겠습니다.