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function amortization_array($principal, $interest_rate, $start_year, $start_month, $term, $group_by = 'M, Y', $month_names){
	$periods  = $term * 12;
	$balance  = $principal;
	$interest = $interest_rate / 100 / 12;
        $payment  = $principal * $interest / (1 - pow((1 + $interest), -$periods));

	for($period = 0; $period < $periods; $period++){
		$date = get_date($start_year, $start_month + $period, $group_by, $month_names);
		$results[$date]['date']       = $date;
		$results[$date]['p']	  = $period + 1;

		$results[$date]['year']       = substr($date, -4);
		$results[$date]['interest']  += $balance * $interest;
		$results[$date]['principal'] += $payment - $balance * $interest;
		$results[$date]['balance']    = $balance = $balance - $payment + $balance * $interest;

		if($results[$date]['balance'] < 0) $results[$date]['balance'] = 0;
	}
	return $results;
}