Sql query with date where clause

[eluser]Todlerone[/eluser]
I was able to get this to work perfectly within the main controller, ie, no helper call.

Code:

$allpts = $this->Stats_model->all_patients();
    $lstmth=0;
    foreach ($allpts as $ap) :
        $month_sel = date('m', strtotime('-1 month'));
        $t = date("m", strtotime($ap['demo_created_on']));
        if ($t == $month_sel){
            $lstmth++;
        }
    endforeach;
    $data['new_patients_current_month'] = $lstmth;

I just want to vary the date('m', strtotime('-3 month')) line several times. How would I go about reusing this code? TY