将已知数组按条件分成若个新数组

$ar = array (
  0 => 
  array (
    'po_num' => 'DYNP-770266110-00',
    'plant' => 'DYNP',
    'get_date' => '2013-09-09',
    'cust_no' => '12654172',
    'total' => '615',
    'snp' => '15',
    'mount' => '41',
    'lp_no' => 'P000000D',
  ),
  1 => 
  array (
    'po_num' => 'DYNP-770266110-00',
    'plant' => 'DYNP',
    'get_date' => '2013-09-09',
    'cust_no' => '12647212',
    'total' => '60',
    'snp' => '15',
    'mount' => '4',
    'lp_no' => 'P000000D',
  ),
);
$split_num = 100;
foreach($ar as $item) {
  if($item['total']     $res[] = $item;
    continue;
  }
  $total = $item['total'];
  $n = ceil($total/$split_num);
  for($i=1; $i    $res[] = array_merge(array('po_nume' => "$i/$n"), $item, array('total' => $split_num));
  }
  $res[] = array_merge(array('po_nume' => "$i/$n"), $item, array('total' => $total%$split_num));
}
print_r($res);

Array
(
    [0] => Array
        (
            [po_nume] => 1/7
            [po_num] => DYNP-770266110-00
            [plant] => DYNP
            [get_date] => 2013-09-09
            [cust_no] => 12654172
            [total] => 100
            [snp] => 15
            [mount] => 41
            [lp_no] => P000000D
        )

    [1] => Array
        (
            [po_nume] => 2/7
            [po_num] => DYNP-770266110-00