Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Financial.php
public static function IPMT($rate, $per, $nper, $pv, $fv = 0, $type = 0)
    {
        $rate = Functions::flattenSingleValue($rate);
        $per = (int) Functions::flattenSingleValue($per);
        $nper = (int) Functions::flattenSingleValue($nper);
        $pv = Functions::flattenSingleValue($pv);
        $fv = Functions::flattenSingleValue($fv);
        $type = (int) Functions::flattenSingleValue($type);

        // Validate parameters
        if ($type != 0 && $type != 1) {
            return Functions::NAN();
        }
        if ($per <= 0 || $per > $nper) {
            return Functions::VALUE();
        }

        // Calculate
        $interestAndPrincipal = self::interestAndPrincipal($rate, $per, $nper, $pv, $fv, $type);

        return $interestAndPrincipal[0];
    }
public static function IPMT($rate, $per, $nper, $pv, $fv = 0, $type = 0)
    {
        $rate = Functions::flattenSingleValue($rate);
        $per = (int) Functions::flattenSingleValue($per);
        $nper = (int) Functions::flattenSingleValue($nper);
        $pv = Functions::flattenSingleValue($pv);
        $fv = Functions::flattenSingleValue($fv);
        $type = (int) Functions::flattenSingleValue($type);

        // Validate parameters
        if ($type != 0 && $type != 1) {
            return Functions::NAN();
        }
        if ($per <= 0 || $per > $nper) {
            return Functions::VALUE();
        }

        // Calculate
        $interestAndPrincipal = self::interestAndPrincipal($rate, $per, $nper, $pv, $fv, $type);

        return $interestAndPrincipal[0];
    }
IPMT.

Returns the interest payment for a given period for an investment based on periodic, constant payments and a constant interest rate.

Excel Function:
IPMT(rate,per,nper,pv[,fv][,type])

@param float $rate Interest rate per period
@param int $per Period for which we want to find the interest
@param int $nper Number of periods
@param float $pv Present Value
@param float $fv Future Value
@param int $type Payment type: 0 = at the end of each period, 1 = at the beginning of each period

@return float