เรียนถามท่านผู้รู้ คือดิฉันต้องการ sum ซ้อนซ้ำ ต้องเขียน code ยังไงค่ะ

$a= 1000+2000+3000+4000; //ได้ค่า 10000
$b= 1000+2000+3000+5000; //ได้ค่า 11000
$sum =$a+$b; //ได้ค่า 21000

echo $sum;

<td width="5%" align="right"><font size="2"><?php echo $jobtype[1][7] ?></font></td>
    <td width="6%" align="right"><font size="2"><?php echo $jobtype[2][7] ?></font></td>
    <td width="5%" align="right"><font size="2"><?php echo $jobtype[3][7] ?></font></td>
    <td width="5%" align="right"><font size="2"><?php echo $jobtype[4][7] ?></font></td>
    <td width="5%" align="right"><font size="2"><?php echo $jobtype[5][7] ?></font></td>
    <td width="5%" align="right"><font size="2"><?php echo $jobtype[6][5] ?></font></td>
    <td width="5%" align="right"><font size="2"><?php echo $jobtype[7][5] ?></font></td>
    <td width="5%" align="right"><font size="2">
      <?php  echo $jobtype[8][7] ?>
    </font></td>
    <td width="5%" align="right"><font size="2"><?php echo $jobtype[9][7] ?></font></td>
    <td width="5%" align="right"><font size="2"><?php echo $jobtype[10][7] ?></font></td>
    <td width="5%" align="right"><font size="2"><?php echo $jobtype[11][7] ?></font></td>
    <td width="5%" align="right"><font size="2"><?php echo $jobtype[12][7] ?></font></td>
    <td width="7%" align="right"><font size="2"><?php echo $sumdi =number_format($jobtype[1][7]+$jobtype[2][7]+$jobtype[3][7]+$jobtype[4][7]+$jobtype[5][7]+$jobtype[6][7]+$jobtype[7][7]+$jobtype[8][7]+$jobtype[9][7]+$jobtype[10][7]+$jobtype[11][7]+$jobtype[12][7],2);?></font></td>
  </tr>
  <tr>
    <td width="4%" align="center"><font size="2">6</font></td>
    <td width="28%" align="left"><font size="2">ค่าใช้จ่ายในการบริหารงานโครงการโดยทางอ้อม</font></td>
    <td align="right"><font size="2"><?php echo $jobtype[1][8] ?></font></td>
    <td align="right"><font size="2"><?php echo $jobtype[2][8] ?></font></td>
    <td align="right"><font size="2"><?php echo $jobtype[3][8] ?></font></td>
    <td align="right"><font size="2"><?php echo $jobtype[4][8] ?></font></td>
    <td align="right"><font size="2"><?php echo $jobtype[5][8] ?></font></td>
    <td align="right"><font size="2"><?php echo $jobtype[6][8] ?></font></td>
    <td align="right"><font size="2"><?php echo $jobtype[7][8] ?></font></td>
    <td align="right"><font size="2">
      <?php  echo $jobtype[8][8] ?>
    </font></td>
    <td align="right"><font size="2"><?php echo $jobtype[9][8] ?></font></td>
    <td align="right"><font size="2"><?php echo $jobtype[10][8] ?></font></td>
    <td align="right"><font size="2"><?php echo $jobtype[11][8] ?></font></td>
    <td align="right"><font size="2"><?php echo $jobtype[12][8] ?></font></td>
    <td align="right"><font size="2"><?php echo $sumind =number_format($jobtype[1][8]+$jobtype[2][8]+$jobtype[3][8]+$jobtype[4][8]+$jobtype[5][8]+$jobtype[6][8]+$jobtype[7][8]+$jobtype[8][8]+$jobtype[9][8]+$jobtype[10][8]+$jobtype[11][8]+$jobtype[12][8],2);?>