how to use increment() and decrement() in laravel

I have a table total_count

+----+--------+-------+------+---------+---------+---------+
| id | studid | month | year | acls_id | total_p | total_a |
+----+--------+-------+------+---------+---------+---------+
| 1  |   30   |  08   | 2015 |   12    |    5    |    2    |
| 2  |   35   |  08   | 2015 |   12    |    5    |    2    |
| 3  |   52   |  08   | 2015 |   12    |    5    |    2    |
| 4  |   53   |  08   | 2015 |   12    |    5    |    2    |
| 5  |   54   |  08   | 2015 |   12    |    5    |    2    |
| 6  |   55   |  08   | 2015 |   12    |    5    |    2    |
| 7  |   30   |  09   | 2015 |   12    |    3    |    0    |
| 8  |   35   |  09   | 2015 |   12    |    3    |    0    |
| 9  |   52   |  09   | 2015 |   12    |    2    |    1    |
| 10 |   53   |  09   | 2015 |   12    |    3    |    0    |
| 11 |   54   |  09   | 2015 |   12    |    3    |    0    |
| 12 |   55   |  09   | 2015 |   12    |    3    |    0    |
+----+--------+-------+------+---------+---------+---------+

I want to increment and decrement for each student total_p and total_a.

when iam edit my student attendance list.

eg:studid 30 total_p = 5 and total_a= 2 ,so iam edit my attendance present become absent .

so want decrement total_p by 1 and increment total_a by 1.

So I'd like to get the total of each month for each studid and a increment and decrement of total_p and total_a for the total months.

My controller code is

if ($present ==0) {
    DB::table($wys_total_attend_table)->where('studid',$student->id)
                                      ->where('smonth','=',$date_exploded[1])
                                      ->where('syear','=',$date_exploded[2])
                                      ->increment('stotal_a', 1)
                                      ->decrement('stotal_p',1);
}
elseif ($present ==1) {
   DB::table($wys_total_attend_table)->where('studid',$student->id)
                                     ->where('smonth','=',$date_exploded[1])
                                     ->where('syear','=',$date_exploded[2])
                                     ->increment('stotal_p', 1)
                                     ->decrement('stotal_a', 1); 
}

but it doesn't work..

How to use increment() and decrement() in query builder format?

for eg:if iam only edit studid =30 attendance increment total_p value 1 and (present==1) studid =30 total_p=6 and total_a=1 and other studid values are old value.

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