/**
* Returns the principal payment for a given period for a cash flow with constant periodic payments (annuities)
* and interest rate
* Excel equivalent: PPMT
*
* @param float Interest rate per period
* @param int Period for which the principal payment will be calculated
* @param int Number of periods
* @param float Present Value
* @param float Future Value
* @param int Payment type:
FINANCE_PAY_END (default): at the end of each period
FINANCE_PAY_BEGIN: at the beginning of each period
* @return float
* @static
* @access public
*/
function principalPayment($rate, $per, $nper, $pv, $fv = 0, $type = 0)
{
if ($type != FINANCE_PAY_END && $type != FINANCE_PAY_BEGIN) {
return PEAR::raiseError('Payment type must be FINANCE_PAY_END or FINANCE_PAY_BEGIN');
}
$interestAndPrincipal = Math_Finance::_interestAndPrincipal($rate, $per, $nper, $pv, $fv, $type);
return $interestAndPrincipal[1];
}
