How to calculate Insurance premium installment

For a car with value of $10,000 with

11% of base premium
17% of commission rate
10% of tax

It would be easy to calculate the one-time Policy amount. But When the Policy amount is to be paid in installment of 6 months, I'm finding it quite difficult to implement.

I tried with following formula in PHP

$princ =21500; //principal amount
$term = 9; //months
$intr =13/ 1200; //get percentage

$EMI= ceil($princ * $intr / (1 - (pow(1/(1 + $intr), $term)))); # This for total EMI

$TOT_INTEREST= ceil(($princ * $intr / (1 - (pow(1/(1 + $intr), $term))))*$term) - $princ; # This is for Total interest

But I don't get it right.

How shall I calculate the Policy installments for each month so that,

• Installment sums must match total policy sum - pay attention to cases where sum does not divide equally
• Separate commission amount and tax amount for each installment