php读取mysql id显示01 02 03

I wanna php output my mysql 1 as 01, 2 as 02.... and so on, so I get database ID first then I wrote this code for output

if ($id <10) {
    echo '0'.$id;
} else {
    echo $id;
}

and then I want to insert $id to my class then in a loop

 while ($sth <100) {
     $id = mysql_result($result,$mtt,"ID");
     echo "<div class='active_$id'>$info</div>";

  $sth++
}

how should i replace

if ($id <10) {
    echo '0'.$id;
} else {
    echo $id;
}

to $id?

You should write:

$id = str_pad($id, 2, "0", STR_PAD_LEFT);

You can use str_pad, or printf.

str_pad($i, 2, '0', STR_PAD_LEFT); // works
printf("%02d", $i); // works too