How to count multiple rows and print the num of rows in php?

Question

There are many students in my table with different classes. I want to print different class one time and print the number of students of that class. I can print the class. But couldn't print the number of students for each class. How can I do this? For example:

In my database:                       Desired Output:

Class     Name                         Class      Num. of Students
  2       John                           1             2
  2       Snow                           2             3
  3       Jara                           3             1
  1       Peter
  1       Nira
  2       Jerin

Here is my code:

        $q = "SELECT * FROM ipsc_student group by class";
        $rs = mysql_query($q);
        $numOfRows=mysql_num_rows($rs);

        $rt = "";

        $sl = 0;
            while($row=mysql_fetch_assoc($rs)){
                $sl++;
                $rt.="<tr>";
                $rt.="<td>$sl</td>";
                $rt.="<td>".$row['class']."</td>";
                $rt.="<td>$numOfRows</td>";
                $rt.="<td></td>";
                $rt.="<td></td>";
                $rt.="<td></td>";
                $rt.="<td></td>";
                $rt.="<td></td>";
                $rt.="<td></td>";
                $rt.="</tr>";
            }
            echo $rt;

Answer 1

Try this

    $q = "SELECT class, count(*) as NUM FROM ipsc_student GROUP BY class";

    $rs = mysql_query($q);
    $numOfRows=mysql_num_rows($rs);

    $rt = "";

    $sl = 0;
        while($row=mysql_fetch_assoc($rs)){
            $sl++;
            $rt.="<tr>";
            $rt.="<td>$sl</td>";
            $rt.="<td>".$row['class']."</td>";
            $rt.="<td>".$row['NUM']."</td>";
            $rt.="<td></td>";
            $rt.="<td></td>";
            $rt.="<td></td>";
            $rt.="<td></td>";
            $rt.="<td></td>";
            $rt.="<td></td>";
            $rt.="</tr>";
        }
        echo $rt;